Electric element and electric circuit

ABSTRACT

Each of the plurality of conductive plates is formed on a principal surface of each of stacked dielectric layers. Side anode electrodes are connected to positive electrodes of conductive plates, while side cathode electrodes are connected to cathodes of conductive plates. Anode electrodes are connected to the side anode electrodes. Cathode electrodes are connected to the side cathode electrodes. By passing DC currents through the positive conductive plates and cathode conductive plates so as to flow in the opposite directions, effective inductance of the positive conductive plates becomes smaller than its self-inductance. Consequently, the inductance is reduced, thereby lowering impedance.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/513,027 filed on Aug. 31, 2006. The priority applications NumbersJP2005-254620, JP2005-254690, JP2005-254750, JP2006-195565, upon whichU.S. application Ser. No. 11/513,027 is based, are hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electric elements and electric circuits, andmore particularly to an electric element and an electric circuitfunctioning as a noise filter with a wide frequency coverage andexcellent high-frequency characteristics.

2. Description of Related Art

Recently, digital circuit technology such as LSI (Large ScaleIntegrated) circuit technology is adopted in not only computers andcommunication-related equipment but also consumer electronics andin-vehicle equipment.

The high-frequency current produced in the LSI circuit or the like doesnot stay in the vicinity of the LSI circuit but flows to the wide areaof a component-mounted circuit board such as a printed-circuit board.The high-frequency current then inductively couples to signal wires andgrounding wires and leaks as an electromagnetic wave from signal cablesor the like.

In mixed-signal circuits in which analog circuitry and digital circuitryare combined, for example, a circuit in which a part of a conventionalanalog circuit is replaced with a digital circuit, and a digital circuithaving analog input/output, one of the serious problems iselectromagnetic interference from the digital circuit to the analogcircuit.

The effective solution of this problem is to separate the LSI circuit,which is a source of the high-frequency current, from a power supplyingsystem with respect to the high frequency, that is to say a “powerdecoupling” technique. Known as a noise filter employing the powerdecoupling technique is a transmission-line type noise filter (e.g.Japanese unexamined patent application No. 2004-80773).

This transmission-line type noise filter comprises a first electricalconductor, a second electrical conductor, a dielectric layer, a firstanode and a second anode. Each first and second electrical conductor isin the form of a plate. The dielectric layer is disposed between thefirst and second electrical conductors.

The first anode is connected to one end of the first electricalconductor in a longitudinal direction, while the second anode isconnected to the other end of the first electrical conductor in thelongitudinal direction. The second electrical conductor functions as acathode to connect to reference potential. The first electricalconductor, dielectric layer, and second electrical conductor constitutea capacitor. The thickness of the first electrical conductor is so setas to substantially prevent the temperature rise caused by a DC (directcurrent) component of the current flowing through the first electricalconductor.

The transmission-line type noise filter is connected between a DC powersource and an LSI circuit so as to feed a DC current from the DC powersource through a path made up of the first anode, the first electricalconductor and the second anode to the LSI circuit, while attenuating anAC (alternating current) current produced in the LSI circuit.

As discussed above, the transmission-line type noise filter has astructure of a capacitor, and uses the first and second electricalconductors, which are two electrodes of the capacitor, as transmissionlines.

BRIEF SUMMARY OF THE INVENTION

However, the transmission-line type noise filter has an impedanceexpressed by (inductance/capacitance)^(1/2), and is not provided with ameans for reducing inductance. The impedance shifts from a region wherethe capacitance is dominant to a region where the inductance is dominantwith an increase in frequency. Accordingly, the conventionaltransmission-line type noise filters cannot have lower impedance thanimpedance determined by inherent inductance of the transmission-linetype noise filters.

When the conventional transmission-line type noise filter, which isconnected between a power source and an electrical load circuit such asa CPU (Central Processing Unit) operating at a predetermined frequency,is used as a decoupling circuit, it is difficult to fully confine anunwanted high-frequency current produced by the electrical load circuitwithin the vicinity of the electrical load circuit. In other words,there is a problem of leakage of the unwanted high-frequency currenttoward the other circuits.

Another problem is the difficulty in rapidly supplying an electriccurrent from the power source to the electrical load circuit in responseto rapid start-up of the electrical load circuit.

The present invention is made to solve the problems and has an object toprovide an electric element capable of reducing impedance by decreasingthe inductance.

The present invention has another object to provide an electric circuitcapable of preventing leakage of an unwanted high-frequency currenttoward the power source.

The present invention has yet another object to provide an electriccircuit enabling rapid start-up of the electrical load circuit aspreventing the leakage of the unwanted high-frequency current toward thepower source.

According to the present invention, the electric element is disposedbetween a power source and an electrical load circuit operating with anelectric current from the power source, and comprises first conductivelayers and second conductive layers. The first conductive layers are aconductor through which a first current flows from the power source sideto the electrical load circuit side. The second conductive layers are aconductor through which a second current, which is a return current ofthe first current, flows from the electrical load circuit side to thepower source side. The first conductor has a smaller inductance than itsself-inductance when the first and second currents flow through thefirst and second conductors, respectively.

Preferably, the first conductor comprises n-number (n is a positiveinteger) of the first conductive layers each in the form of a flatplate, while the second conductor comprises m-number (m is a positiveinteger) of the second conductive layers each in the form of a flatplate and opposed to the first conductive layers. The n-number of firstconductive layers and m-number of second conductive layers arealternately stacked.

Preferably, the electric element further comprises dielectrics. Eachdielectric layer is disposed between a first conductive layer and asecond conductive layer. Each of the n-number of first conductive layerspasses the first current, which is an electric current from the powersource, and is sandwiched between two second conductive layers connectedto ground potential.

Preferably, the first current flows in the opposite direction to thesecond current.

Preferably, where the length of the first and second conductive layer inthe direction perpendicular to the direction in which the first andsecond currents flow is W, and the length of the first and secondconductive layers along the direction in which the first and secondcurrents flow is L, an overlap part between the first conductive layerand second conductive layer holds W≧L.

Preferably, the electric element further comprises first to fourthelectrodes. The first electrode is electrically connected to one end ofthe n-number of first conductive layers in a first direction in whichthe first current flows in the first conductive layers. The secondelectrode is electrically connected to the other end of the n-number offirst conductive layers in the first direction. The third electrode iselectrically connected to one end of the m-number of second conductivelayers in a second direction in which the second current flows in thesecond conductive layers. The fourth electrode is electrically connectedto the other end of the m-number of second conductive layers in thesecond direction.

According to the present invention, the electric element is in the formof an approximately rectangular parallelepiped and comprises a pluralityof first conductive layers, a plurality of second conductive layers, aplurality of dielectrics, and first to fourth electrodes. The pluralityof first conductive layers are disposed approximately parallel to thebottom face of the rectangular parallelepiped. The plurality of secondconductive layers are disposed approximately parallel to the bottom faceof the rectangular parallelepiped. Each of the plurality of dielectricsis disposed between a first conductive layer and a second conductivelayer. The first electrode is connected to one end of the plurality offirst conductive layers. The second electrode is connected to the otherend of the plurality of first conductive layers. The third electrode isconnected to the plurality of second conductive layers in the proximityof one end of the second conductive layers. The fourth electrode isconnected to the plurality of second conductive layers in the proximityof the other end of second conductive layers.

Preferably, the first conductive layers are longer than the secondconductive layers in a first direction from a first side face disposedapproximately vertically on the bottom face of the rectangularparallelepiped to a second side face opposed to the first side face,while the second conductive layers are longer than the first conductivelayers in a second direction from a third side face disposedapproximately vertically on the bottom face of the rectangularparallelepiped and approximately perpendicular to the first and secondside faces to a fourth side face opposed to the third side face.

Preferably, the first conductive layers are longer than the secondconductive layers in a first direction from a first side face disposedapproximately vertically on the bottom face of the rectangularparallelepiped to a second side face opposed to the first side face,while having approximately the same dimension as the second conductivelayers in a second direction from a third side face disposedapproximately vertically on the bottom face of the rectangularparallelepiped and approximately perpendicular to the first and secondside faces to a fourth side face opposed to the third side face. Thesecond conductive layers have extending portions each connected to thethird and fourth electrodes.

Preferably, the first electrode is connected to the plurality of firstconductive layers on the first side face, while the second electrode isconnected to the plurality of first conductive layers on the second sideface. The third electrode is connected to the plurality of secondconductive layers at positions closer to the first side face than themidpoint between the first side face and the second side face, on thethird and fourth side faces, while the fourth electrode is connected tothe plurality of second conductive layers at a position closer to thesecond side face than the midpoint, on the third and fourth side faces.

Preferably, the first conductive layers has approximately the samedimension as the second conductive layers in a first direction from afirst side face disposed approximately vertically on the bottom face ofthe rectangular parallelepiped to the second side face opposed to thefirst side face, and in a second direction from a third side facedisposed approximately vertically on the bottom face of the rectangularparallelepiped and approximately perpendicular to the first and secondside faces to a fourth side face opposed to the third side face. Thefirst conductive layers have first and second extending portionsextending toward the first and the second side faces, respectively,while the second conductive layers have third and fourth extendingportions extending toward the first and the second side faces,respectively.

Preferably, the first electrode is connected to the first extendingportions of the plurality of first conductive layers on the first sideface, while the second electrode is connected to the second extendingportions of the plurality of first conductive layers on the second sideface. The third electrode is connected to the third extending portionsof the plurality of second conductive layers on the first side face,while the fourth electrode is connected to the fourth extending portionsof the plurality of second conductive layers on the second side face.

Preferably, the first extending portions are formed closer to the thirdside face than the midpoint between the third side face and the fourthside face in the second direction, while the second extending portionsare formed closer to the fourth side face than the midpoint in thesecond direction. The third extending portions are formed closer to thefourth side face than the midpoint in the second direction, while thefourth extending portions are formed closer to the third side face thanthe midpoint in the second direction.

Preferably, the first conductive layer has approximately the samedimension as the second conductive layer in a first direction from afirst side face disposed approximately vertically on the bottom face ofthe rectangular parallelepiped to the second side face opposed to thefirst side face, and in a second direction from a third side facedisposed approximately vertically on the bottom face of the rectangularparallelepiped and approximately perpendicular to the first side faceand the second side face to a fourth side face opposed to the third sideface. The first conductive layers have first and second extendingportions extending toward the third side face, while the secondconductive layers have third and fourth extending portions extendingtoward the fourth side face.

Preferably, the first electrode is connected to the first extendingportions of the plurality of first conductive layers on the third sideface, while the second electrode is connected to the second extendingportions of the plurality of first conductive layers on the third sideface. The third electrode is connected to the third extending portionsof the plurality of second conductive layers on the fourth side face,while the fourth electrode is connected to the fourth extending portionsof the plurality of second conductive layers on the fourth side face.

Preferably, where the length of the first and second conductive layersin the first direction is W and the length of first and secondconductive layers in the second direction is L, an overlap part betweenthe first conductive layer and second conductive layer holds W≧L.

Preferably, where the length of first and second conductive layers inthe first direction is W and the length of first and second conductivelayers in the second direction is L, an overlap part between the firstconductive layer and second conductive layer holds L>W.

Preferably, the first and second conductive layers are composed ofmetallic materials containing nickel as a main material. The dielectricsare composed of ceramic materials containing BaTiO₃ as a main material.

An electric circuit according to the present invention includes any oneof electric elements disclosed in the present invention disposed betweena power source and an electrical load. The plurality of first conductivelayers constitute a path through which the first current flows from thepower source side to the load side, while the plurality of secondconductive layers constitute a path through which the second current asa return current of the first current flows.

The electric circuit according to the present invention further includesan electric element connected to the power source and a capacitorconnected between the electric element and the electrical load. Theelectric element is any one of electric elements disclosed in thepresent invention.

Preferably, the first electrode of the electric element is connected toa positive electrode of the power source. The second electrode of theelectric element is connected to an anode of the capacitor. The thirdelectrode of the electric element is connected to a cathode of thecapacitor. The fourth electrode of the electric element is connected toa negative electrode of the power source. The anode of the capacitor isconnected to a positive electrode of the electrical load. The cathode ofthe capacitor is connected to a negative electrode of the electricelement.

The electric circuit according to the present invention includes a firstelectric element having an approximately rectangular plane and connectedto the power source, and a second electric element having theapproximately rectangular plane and connected to the electrical load. Afirst dimension of the first electric element in a lateral direction ofthe rectangle is longer than a second dimension of the first electricelement in a vertical direction of the rectangle, while the thirddimension of the second electric element in the lateral direction of therectangle is shorter than a fourth dimension of the second electricelement in the vertical direction of the rectangle.

In the present invention, when the first and second currents flow in thefirst and second conductors, respectively, the inductance of the firstconductor becomes smaller than its self-inductance by mutual inductancebetween the first conductor and the second conductor. Thus, impedance ofthe electric element is reduced with the decrease in inductance of thefirst conductor.

The present invention can thus reduce impedance through the reduction ofthe inductance.

According to the present invention, the electric element comprises aplurality of first conductive layers, a plurality of second conductivelayers, a plurality of dielectrics, first to fourth electrodes. Each ofthe plurality of dielectrics is disposed between a first conductivelayer and a second conductive layer. The first and second electrodes areconnected to the plurality of first conductive layers at opposite endsthereof, while the third and fourth electrodes are connected to theplurality of second conductive layers at the opposite ends thereof. Thisconfiguration allows an electric current to flow through the firstelectrode, plurality of first conductive layers and second electrode inthis order and allows a return current of the electric current to flowthrough the fourth electrode, plurality of second conductive layers andthird electrode in this order. Because the first conductive layers andsecond conductive layers have the electric current flowed in theopposite direction to each other, the inductance of the first conductivelayer becomes smaller than its self-inductance by mutual inductancebetween the first and second conductive layers.

The present invention can thus reduce impedance through the reduction ofinductance.

According to the present invention, the electric circuit comprises anelectric element disposed between a power source and an electrical load.The electric element confines an unwanted high-frequency currentproduced by the electrical load within circuitry built up with theelectrical load and electric element.

The present invention can thus prevent the unwanted high-frequencycurrent from leaking toward the power source.

According to the present invention, an electric circuit comprises anelectric element connected to a power source and a capacitor connectedbetween the electric element and an electrical load. The electriccircuit stores power source currents supplied from the power source tosupply the stored power source current to the electrical load, whileconfining the unwanted high-frequency current produced by the electricalload within circuitry built up with the electrical load and electricelement.

Thus, the present invention can prevent the unwanted high-frequencycurrent from leaking toward the power source and enable to rapidlysupply the power source current to the electrical load circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating the structure of an electricelement according to the first embodiment of the present invention.

FIG. 2 a diagram for describing dimensions of dielectric layers andconductive plates shown in FIG. 1.

FIG. 3 is a plan view illustrating two adjacent conductive plates.

FIGS. 4A and 4B are cross-sectional views of the electric element shownin FIG. 1.

FIGS. 5A to 5C are the first process drawings for describing afabricating method of the electric element shown in FIG. 1

FIGS. 6A and 6B are the second process drawings for describing afabricating method of the electric element shown in FIG. 1

FIG. 7 is a perspective view for describing the functions of theelectric element shown in FIG. 1.

FIG. 8 is a view for describing magnetic flux density produced by anelectric current passing through a conductive wire.

FIG. 9 is a view for describing effective inductance upon the occurrenceof magnetic interference between two conductive wires.

FIG. 10 is a schematic view illustrating the structure of anotherelectric element according to the first embodiment of the presentinvention.

FIG. 11 is a conceptual illustration showing the electric element shownin FIG. 1 in an operating state.

FIG. 12 illustrates the frequency-dependent attenuation characteristicsin the electric element shown in FIG. 1.

FIG. 13 is a view illustrating the frequency dependence of impedance inthe electric element shown in FIG. 1.

FIG. 14 is another view illustrating the frequency dependence ofimpedance in the electric element shown in FIG. 1.

FIG. 15 is yet another view illustrating the frequency dependence ofimpedance in the electric element shown in FIG. 1.

FIG. 16 is yet another view illustrating the frequency dependence ofimpedance in the electric element shown in FIG. 1.

FIG. 17 is a schematic view illustrating the structure of an electricelement according to the second embodiment.

FIGS. 18A to 18E are plan views of dielectric layers and conductiveplates shown in FIG. 17 and a bottom view of the electric element shownin FIG. 17.

FIG. 19 is a schematic view illustrating the structure of an electricelement according to the third embodiment.

FIGS. 20A to 20E are plan views of the dielectric layers and conductiveplates shown in FIG. 19 and a bottom view of the electric element shownin FIG. 19.

FIG. 21 is a schematic view illustrating the structure of an electricelement according to the fourth embodiment.

FIGS. 22A to 22E are plan views of the dielectric layers and conductiveplates shown in FIG. 21 and a bottom view of the electric element shownin FIG. 21.

FIG. 23 is a schematic view illustrating the first modification of theelectric element according to the embodiments of the present invention.

FIG. 24 is a plan view of the electric element shown in FIG. 23.

FIG. 25 is a schematic view illustrating the second modification of theelectric element according to the embodiments of the present invention.

FIGS. 26A and 26B are side views of the electric element shown in FIG.25.

FIG. 27 is a schematic view illustrating the third modification of theelectric element according to the embodiments of the present invention.

FIGS. 28A and 28B are a plan view and a side view, respectively,illustrating the electric element shown in FIG. 27.

FIG. 29 is a schematic view illustrating the fourth modification of theelectric element according to the embodiments of the present invention.

FIG. 30 is a plan view of the electric element viewed from direction Cin FIG. 29.

FIG. 31 is a schematic view illustrating the structure of an electriccircuit according to the fifth embodiment.

FIG. 32 is a schematic view illustrating the structure of an electriccircuit according to the sixth embodiment.

FIG. 33 is a conceptual illustration showing the electric element shownin FIG. 32 in an operating state.

FIG. 34 is a perspective view illustrating the structure of thecapacitor shown in FIG. 32.

FIG. 35 is an another schematic view illustrating the structure of anelectric circuit according to the sixth embodiment.

FIG. 36 is a cross-sectional view illustrating the electric element andcapacitor shown in FIG. 35.

FIG. 37 is a perspective view illustrating an exemplary electric circuitaccording to the sixth embodiment.

FIG. 38 is a plan view of the electric circuit viewed from direction Ain FIG. 37.

FIG. 39 is a plan view of the electric circuit viewed from direction Bin FIG. 37.

FIG. 40 is a plan view of the electric circuit viewed from direction Cin FIG. 37.

FIG. 41 is a cross-sectional view of the electric circuit taken alongline XXXXI-XXXXI in FIG. 37.

FIG. 42 is a schematic view illustrating the structure of the electriccircuit according to the seventh embodiment.

FIG. 43 is a bottom view illustrating the electric element shown in FIG.42.

FIG. 44 is a plan view illustrating a board on which the electriccircuit shown in FIG. 42 is mounted.

FIG. 45 is a schematic view illustrating the structure of the otherelectric circuits according to the seventh embodiment.

FIG. 46 is a plan view of the two electric elements shown in FIG. 45.

FIG. 47 is a side view of the electric circuit shown in FIG. 45 viewedfrom direction A.

FIG. 48 is a bottom view of the electric circuit shown in FIG. 45.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when reviewed in conjunction withthe accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, a detailed description will be made onembodiments of the present invention. Components identical or equivalentto each other in the drawings are denoted by the same reference number,and will not be further explained to avoid repetition.

The First Embodiment

FIG. 1 is a schematic view illustrating the structure of an electricelement according to the first embodiment of the present invention.Referring to FIG. 1, the electric element 100 of the first embodiment ofthe present invention is in the form of an approximately rectangularparallelepiped and comprises dielectric layers 1 to 5, conductive plates11, 12, 21 to 23, side anode electrodes 10A, 10B, anode electrodes 10C,10D, side cathode electrodes 20A, 20B, 20C, 20D, and cathode electrodes20E, 20F.

The dielectric layers 1 to 5 are stacked in sequence. The conductiveplates 11, 12, 21 to 23 are in the form of a flat plate each. Theconductive plate 21 is placed between the dielectric layers 1 and 2,while the conductive plate 11 is placed between the dielectric layers 2and 3. The conductive plate 22 is placed between the dielectric layers 3and 4, while the conductive plate 12 is placed between the dielectriclayers 4 and 5. The conductive plate 23 is placed on a principal surface5A of the dielectric layer 5. The dielectric layers 1 to 5 support theconductive plates 21, 11, 22, 12, and 23, respectively. The conductiveplates 11, 12, 21 to 23 are arranged approximately parallel to thebottom face (100C) of the rectangular parallelepiped.

The side anode electrode 10A is connected to one end of the conductiveplates 11, 12, and formed on a side face 100A (which is made up of theside faces of the dielectric layers 1 to 4) of the electric element 100.The side anode electrode 10B is connected to the other end of theconductive plates 11, 12, and formed on a side face 100B (which is madeup of the side faces of the dielectric layers 1 to 4) opposed to theside face 100A of the electric element 100. The side anode electrode 10Bis opposed to the side anode electrode 10A.

The anode electrode 10C is disposed on the bottom face 100C of theelectric element 100 and connected to the side anode electrode 10A. Theanode electrode 10D is disposed on the bottom face 100C of the electricelement 100 and connected to the side anode electrode 10B.

The side cathode electrode 20A is connected to the conductive plates 21to 23 in the proximity of one end of the conductive plates 21 to 23 anddisposed on the front face 100D of the electric element 100. The sidecathode electrode 20B is connected to the conductive plates 21 to 23 inthe proximity of one end of the conductive plates 21 to 23 and disposedon the rear face 100E opposite to the front face 100D of the electricelement 100. The side cathode electrode 20B is opposed to the sidecathode electrode 20A.

The side cathode electrode 20C is connected to the conductive plates 21to 23 in the proximity of the other end of the conductive plates 21 to23 and disposed on the front face 100D of the electric element 100. Theside cathode electrode 20D is connected to the conductive plates 21 to23 in the proximity of the other end of the conductive plates 21 to 23and disposed on the rear face 100E opposite to the front face 100D ofthe electric element 100. The side cathode electrode 20D is opposed tothe side cathode electrode 20C.

The cathode electrode 20E is connected to the side cathode electrodes20A and 20B and arranged on the bottom face 100C of the electric element100. The cathode electrode 20F is connected to the side cathodeelectrodes 20C and 20D and arranged on the bottom face 100C of theelectric element 100.

As described above, the electric element 100 has the conductive plates11, 12, 21 to 23 alternately disposed with the dielectric layers 1 to 5interposed therebetween, and includes the two anode electrodes 10C, 10Dand two cathode electrodes 20E, 20F.

The dielectric layers 1 to 5 are composed of, for example, bariumtitanate (BaTiO₃). The side anode electrodes 10A, 10B, anode electrodes10C, 10D, conductive plates 11, 12, 21 to 23, side cathode electrodes20A, 20B, 20C, 20D and cathode electrodes 20E, 20F are composed of, forexample, nickel (Ni).

FIG. 2 is a diagram for describing the dimensions of the dielectriclayers 1, 2 and conductive plates 11, 21 shown in FIG. 1. Referring toFIG. 2, each of the dielectric layers 1, 2 has a length of L1 along thedirection DR1, which is the direction of a current flowing in theconductive plates 11, 21, a width of W1 along the direction DR2perpendicular to the direction DR1, and a thickness of D1. The lengthL1, width W1, and thickness D1 are set, for example, at 15 mm, 13 mm,and 25 μm, respectively.

The conductive plate 11 has length L1 and width W2. Width W2 is set, forexample, at 11 mm. The conductive plate 21 has length L2 and width W1.Length L2 is set, for example, at 13 mm. Each of the conductive plates11, 21 has a thickness, for example, in a range between 10 μm to 20 μm.

Each of the dielectric layers 3 to 5 has the same length L1, width W1,and thickness D1 as those of the dielectric layers 1, 2 shown in FIG. 2.The conductive plate 12 has the same length L1, width W2 and thicknessas those of the conductive plate 11 shown in FIG. 2. Each of theconductive plates 22, 23 has the same length L2, width W1, and thicknessas those of the conductive plate 21 shown in FIG. 2.

As discussed above, the dielectric layers 1 to 5 and conductive plates11, 12, 21 to 23 have approximately rectangular planes. The conductiveplates 11, 12 are different in length and width from the conductiveplates 21 to 23. These differences are made to prevent shorting betweenthe side anode electrodes 10A, 10B connected to the conductive plates11, 12 and the side cathode electrodes 20A, 20B, 20C, 20D connected tothe conductive plates 21 to 23.

FIG. 3 is a plan view illustrating two adjacent conductive plates.Suppose the conductive plate 11 and conductive plate 21 are in oneplane, with reference to FIG. 3, the conductive plates 11 and 21 have anoverlap part 20. The overlap part 20 between the conductive plate 11 andconductive plate 21 has length L2 and width W2. Overlap parts betweenthe conductive plate 11 and conductive plate 22, between the conductiveplate 12 and conductive plate 22, and between the conductive plate 12and conductive plate 23 have the same length L2 and width W2 as those ofthe overlap part 20. In the present invention, when the electric element100 functions mainly as a noise filter, length L2 and width W2 are setso as to hold L2>W2. When the electric element 100 functions mainly as acapacitor, length L2 and width W2 are set so as to establish W2≧L2.

FIGS. 4A and 4B are cross-sectional views of the electric element 100shown in FIG. 1. FIG. 4A is a cross-sectional view of the electricelement 100 as taken along line IVA-IVA of FIG. 1, while FIG. 4B is across-sectional view of the electric element 100 as taken along lineIVB-IVB of FIG. 1.

Referring to FIG. 4A, the conductive plate 21 is in contact with bothdielectric layers 1 and 2, while the conductive plate 11 is in contactwith both dielectric layers 2 and 3. The conductive plate 22 is incontact with both dielectric layers 3 and 4, while the conductive plate12 is in contact with both dielectric layers 4 and 5. In addition, theconductive plate 23 is in contact with the dielectric layer 5.

The side cathode electrodes 20C, 20D are not connected to the conductiveplates 11, 12, but to the conductive plates 21 to 23. The cathodeelectrode 20F is disposed under the underside 1A of the dielectric layer1 and connected to the side cathode electrodes 20C, 20D.

Referring to FIG. 4B, the side anode electrodes 10A, 10B are notconnected to the conductive plates 21 to 23, but to the conductiveplates 11, 12. The anode electrodes 10C, 10D are disposed under theunderside 1A of the dielectric layer 1 and connected to the side anodeelectrodes 10A, 10B, respectively.

As a result, a group of conductive plate 21, dielectric layer 2 andconductive plate 11, a group of the conductive plate 11, dielectriclayer 3 and conductive plate 22, a group of the conductive plate 22,dielectric layer 4 and conductive plate 12, and a group of theconductive plate 12, dielectric layer 5 and conductive plate 23constitute four capacitors connected in parallel between the anodeelectrodes 10C and 10D and between the cathode electrodes 20E and 20F.

Each capacitor has an electrode area equal to the overlap part 20 (seeFIG. 3) of the two adjacent conductive plates.

As discussed above, the electric element 100 comprises the conductiveplates 11, 12 disposed parallel to the bottom face 100C of theapproximately rectangular parallelepiped, the conductive plates 21 to 23disposed parallel to the bottom face 100C of the approximatelyrectangular parallelepiped, the dielectric layers 1 to 5 each disposedbetween either of the conductive plate 11 or 12 and any of theconductive plates 21 to 23, the side anode electrode 10A and anodeelectrode 10C connected to one end of the conductive plates 11, 12, theside anode electrode 10B and anode electrode 10D connected to the otherend of the conductive plates 11, 12, the side cathode electrodes 20A,20B and cathode electrode 20E connected to the conductive plates 21 to23 in the proximity of one end of the conductive plates 21 to 23, andthe side cathode electrodes 20C, 20D and cathode electrode 20F connectedto the conductive plates 21 to 23 in the proximity of the other end ofthe conductive plates 21 to 23. The side anode electrode 10A isconnected to the conductive plates 11, 12 on the side face 100A, whilethe side anode electrode 10B is connected to the conductive plates 11,12 on the side face 100B opposed to the side face 100A. The side cathodeelectrode 20A is connected to the conductive plates 21 to 23 on thefront face 100D arranged approximately perpendicular to the side faces100A, 100B and approximately vertically to the bottom face 100C, whilethe side cathode electrode 20B is connected to the conductive plates 21to 23 on the rear face 100E opposed to the front face 100D which isarranged approximately perpendicular to the side faces 100A, 100B andapproximately vertically on the bottom face 100C. The side cathodeelectrode 20C is connected to the conductive plates 21 to 23 on thefront face 100D approximately perpendicular to the side faces 100A, 100Band approximately vertically on the bottom face 100C, while the sidecathode electrode 20D is connected to the conductive plates 21 to 23 onthe rear face 100E opposed to the front face 100D which is arrangedapproximately perpendicular to the side faces 100A, 100B andapproximately vertically on the bottom face 100C.

In the electric element 100, the side anode electrode 10A and anodeelectrode 10C constitute “a first electrode”. The side anode electrode10B and anode electrode 10D constitute “a second electrode”. The sidecathode electrodes 20A, 20B and cathode electrode 20E constitute “athird electrode”. The side cathode electrodes 20C, 20D and cathodeelectrode 20F constitute “a fourth electrode”.

FIGS. 5A to 5C and FIGS. 6A and 6B are the first and second processdrawings, respectively, for describing a fabricating method of theelectric element 100 shown in FIG. 1. Referring to FIGS. 5A to 5C, agreen sheet, which will be the dielectric layer 1 (BaTiO₃), having alength of L1, width of W1 and thickness of D1 is prepared. In an areahaving length L2 and width W1 on the front face 1B of the green sheet,Ni paste is applied by screen printing to form a Ni conductive plate 21.

Similarly, after the dielectric layers 3, 5 composed of BaTiO₃ areprepared, the conductive plates 22, 23 composed of Ni are formed on theprepared dielectric layers 3, 5, respectively (see FIG. 5A).

Subsequently, a green sheet, which will be the dielectric layer 2(BaTiO₃), having length L1, width W1 and thickness D1 are prepared. Inan area having length L1 and width W2 on the front face 2A of the greensheet, Ni paste is applied by screen printing to form a Ni conductiveplate 11.

Similarly, after the dielectric layer 4 composed of BaTiO₃ is prepared,the conductive plate 12 composed of Ni is formed on the prepareddielectric layer 4 (see FIG. 5B).

The green sheets of the dielectric layers 1 to 5 on which conductiveplates 21, 11, 22, 12, and 23 are formed respectively, are successivelylaminated (see FIG. 5C). This successive lamination results in alternatelamination of the conductive plates 11, 12 to be connected to the anodeelectrodes 10C, 10D and the conductive plates 21 to 23 to be connectedto the cathode electrodes 20E, 20F.

Then, the Ni paste is applied by the screen printing to form the sideanode electrodes 10A, 10B, anode electrodes 10C, 10D, side cathodeelectrodes 20A, 20B, 20C, 20D and cathode electrodes 20E, 20F (see FIGS.6A and 6B). The element fabricated as shown in FIG. 6B is fired at atemperature of 1350 degrees C. to complete the electric element 100.Alternatively, the side electrodes (external electrodes) can be made ofmaterials having a lower melting point and higher conductivity than thatof the internal electrodes (conductive plates 11, 12, 21 to 23) by useof post-fire. Further, the fired side electrodes (external electrodes)may require plating with Ni, Au, Su or other materials, if necessary,under consideration of solder wettability.

There is another method of fabricating the electric element 100 withoutthe green sheets. In the method, a process of printing and dryingdielectric paste and a process of printing a conductor on the drieddielectric paste are repeatedly performed to stack the dielectric layersand conductive plates.

FIG. 7 is a perspective view for describing the functions of theelectric element 100 shown in FIG. 1. Referring to FIG. 7, with thecathode electrodes 20E, 20F connected to ground potential, the electricelement 100 passes the DC current so that the DC current flows in theconductive plates 11, 12 in the opposite direction to the DC currentflowing in the conductive plates 21 to 23.

If a DC current is fed to the electric element 100 so as to flow fromthe anode electrode 10C to the anode electrode 10D, for example, the DCcurrent flows from the anode electrode 10C through the side anodeelectrode 10A to the conductive plates 11, 12, passes through theconductive plates 11, 12 in the direction of arrow 30, and furtherpasses through the side anode electrode 10B to the anode electrode 10D.

A return current of the current having flowed in the conductive plates11, 12 passes from the cathode electrode 20F through the side cathodeelectrodes 20C, 20D to the conductive plates 21 to 23. The returncurrent then passes through the conductive plates 21 to 23 in thedirection of arrow 40, which is opposite to the arrow 30, and furtherflows in the side cathode electrodes 20A, 20B to the cathode electrode20E.

In this configuration, the DC current I1 flowing through the conductiveplates 11, 12 and the DC current I2 flowing through the conductiveplates 21 to 23 are equal in magnitude and opposite in direction.

FIG. 8 is a view for describing magnetic flux density produced by anelectric current passing through a conductive wire. FIG. 9 is a view fordescribing effective inductance upon the occurrence of magneticinterference between two conductive wires.

Referring to FIG. 8, when an electric current I is flowing in aninfinitely long straight wire, a magnetic flux density B at a point P atdistance a from the wire is expressed by:

$\begin{matrix}{B = \frac{\mu_{0}I}{2\pi\; r}} & (1)\end{matrix}$

In this expression, μ₀ indicates magnetic permeability in a vacuum.

Alternatively, when the conductive wire shown in FIG. 8 is replaced withtwo conductive wires that mutually cause magnetic interference, mutualinductance L₁₂ is expressed as below, where self-inductances of the twowires are L₁₁ and L₂₂, respectively, and coupling coefficient isk(0<k<1), and the mutual inductance of the two conductive wires is L₁₂.L ₁₂ =k·√{square root over (L ₁₁ ·L ₂₂)}  (2)

If L₁₁=L₂₂, the mutual inductance L₁₂ is expressed by:L ₁₂ =k·L ₁₁  (3)

Referring to FIG. 9, given that a conductive wire A and conductive wireB are connected by a lead wire C and both have an electric currentflowing therethrough that are equal in magnitude but opposite indirection, effective inductance L_(11effective) of the conductive wire Ais expressed by:L _(11effective) =L ₁₁ −L ₁₂  (4)

As discussed above, the magnetic interference occurred between theconductive wire A and conductive wire B creates the mutual inductanceL₁₂, which causes the effective inductance L_(11effective) of theconductive wire A to be smaller than the self-inductance L₁₁ of theconductive wire A. This is because the direction of magnetic flux φ_(A)produced by the electric current I flowing in the conductive wire A isopposite to the direction of magnetic flux φ_(B) produced by theelectric current −I flowing in the conductive wire B, thereforeeffective magnetic flux density produced by the electric current I inthe conductive wire A is reduced.

In the above-discussed electric element 100, the conductive plate 11 islocated 25 μm away from the conductive plates 21, 22 and the conductiveplate 12 is located 25 μm away from the conductive plates 22, 23.Because of this, magnetic interference occurs between the conductiveplate 11 and each conductive plate 21 and 22 and between the conductiveplate 12 and each conductive plate 22 and 23. Since the DC current I1flowing in the conductive plates 11, 12 and the DC current I2 flowing inthe conductive plates 21 to 23 are equal in magnitude but opposite indirection, the effective inductance of the conductive plates 11, 12becomes smaller than the self-inductance of the conductive plates 11, 12due to the mutual inductance between the conductive plates 11, 12 andthe conductive plates 21 to 23.

As a result, the effective inductance L of the entire electric element100 is reduced.

The above-discussed electric element 100 with four capacitors connectedin parallel results in having more effective capacitance C as comparedwith an electric element with one capacitor.

In conclusion, the electric element 100 can reduce its impedance with anincrease in the effective capacitance C in a low-frequency rangedominated by capacitance, while the electric element 100 can reduce itsimpedance with a decrease in the effective inductance L in ahigh-frequency range dominated by inductance.

As a result, the electric element 100 has relatively low impedance forbroadband frequencies.

FIG. 10 is a schematic view illustrating the structure of anotherelectric element according to the first embodiment. The electric elementof the first embodiment may be replaced with an electric element 101shown in FIG. 10. Referring to FIG. 10, the conductive plate 23 providedin the electric element 100 shown in FIG. 1 is removed from the electricelement 101. The electric element 101 includes an anode electrode 120instead of the side anode electrode 10A and anode electrode 10C, ananode electrode 130 instead of the side anode electrode 10B and anodeelectrode 10D and all other components included in the electric element100.

The anode electrode 120 is composed of nickel (Ni) and arranged on theside face 100A, and a part of the bottom face 100C, front face 100D,rear face 100E and top face 100F of the electric element 101. Morespecifically, the anode electrode 120 includes a side anode electrode121 and strip electrodes 122 to 125. The side anode electrode 121 isdisposed all over the side face 100A of the electric element 101. Thestrip electrode 122 is disposed on the bottom face 100C of the electricelement 101 and in the proximity of one end of the conductive plates 11,12, 21, 22. The strip electrode 123 is disposed on the front face 100Dof the electric element 101 and in the proximity of one end of theconductive plates 11, 12, 21, 22. The strip electrode 124 is disposed onthe top face 100F of the electric element 101 and in the proximity ofone end of the conductive plates 11, 12, 21, 22. The strip electrode 125is disposed on the rear face 100E of the electric element 101 and in theproximity of one end of the conductive plates 11, 12, 21, 22. The sideanode electrode 121 is connected to one end of the conductive plates 11,12.

The anode electrode 130 is composed of nickel (Ni) and arranged on theside face 100B, and a part of the bottom face 100C, front face 100D,rear face 100E and top face 100F of the electric element 101. Morespecifically, the anode electrode 130 includes a side anode electrode131 and strip electrodes 132 to 135. The side anode electrode 131 isdisposed all over the side face 100B of the electric element 101. Thestrip electrode 132 is disposed on the bottom face 100C of the electricelement 101 and in the proximity of the other end of the conductiveplates 11, 12, 21, 22. The strip electrode 133 is disposed on the frontface 100D of the electric element 101 and in the proximity of the otherend of the conductive plates 11, 12, 21, 22. The strip electrode 134 isdisposed on the top face 100F of the electric element 101 and in theproximity of the other end of the conductive plates 11, 12, 21, 22. Thestrip electrode 135 is disposed on the rear face 100E of the electricelement 101 and in the proximity of the other end of the conductiveplates 11, 12, 21, 22. The side anode electrode 131 is connected to theother end of the conductive plates 11, 12.

FIG. 11 is a conceptual illustration showing the electric element 100shown in FIG. 1 in an operating state. Referring to FIG. 11, theelectric element 100 is connected between a power source 90 and a CPU(Central Processing Unit) 110. The electric element 100 has cathodeelectrodes 20E, 20F connected to ground potential. The power source 90has a positive terminal 91 and negative terminal 92. The CPU 110 has apositive terminal 111 and negative terminal 112.

A lead wire 121 has one end connected with the positive terminal 91 ofthe power source 90 and the other end connected with the anode electrode10C of the electric element 100. A lead wire 122 has one end connectedwith the negative terminal 92 of the power source 90 and the other endconnected with the cathode electrode 20E of the electric element 100.

A lead wire 123 has one end connected with the anode electrode 10D ofthe electric element 100 and the other end connected with the positiveterminal 111 of the CPU 110. A lead wire 124 has one end connected withthe cathode electrode 20F of the electric element 100 and the other endconnected with the negative terminal 112 of the CPU 110.

With this configuration, the DC current I output from the positiveterminal 91 of a power source 90 passes through the lead wire 121 to theanode electrode 10C of the electric element 100, and then passes theside anode electrode 10A, conductive plates 11, 12, side anode electrode10B and anode electrode 10D in this order inside the electric element100. The DC current I flows from the anode electrode 10D to the CPU 110through the lead wire 123 and positive terminal 111.

This passage allows the DC current I to be supplied as a power sourcecurrent to the CPU 110. The CPU 110 is driven with the DC current I andoutputs a return current Ir, which has the same magnitude as the DCcurrent I, from the negative terminal 112.

The return current Ir flows through the lead wire 124 to the cathodeelectrode 20F of the electric element 100, and passes the side cathodeelectrodes 20C, 20D, conductive plates 21 to 23, side cathode electrodes20A, 20B, and cathode electrode 20E in this order inside the electricelement 100. The return current Ir then flows from the cathode electrode20E, through the lead wire 122 and negative terminal 92, to the powersource 90.

Since the DC current I thus flows through the conductive plates 11, 12from the power source 90 side to the CPU 110 side, while the returncurrent Ir flows through the conductive plates 21 to 23 from the CPU 110side to the power source 90 side, the effective inductance L of theelectric element 100 decreases as discussed above. On the other hand,the effective capacitance C of the electric element 100 increases due tothe four parallel-connected capacitors of the electric element 100.

As a result, the impedance of the electric element 100 is reduced.

The CPU 110 is driven with the DC current I supplied from the powersource 90 through the electric element 100, and produces an unwantedhigh-frequency current. This unwanted high-frequency current leaksthrough the lead wire 123, 124 out to the electric element 100. However,the low impedance of the electric element 100 as discussed above causesthe unwanted high-frequency current to flow within circuitry made up ofthe electric element 100 and CPU 110, thereby preventing the leakagefrom the electric element 100 toward the power source 90.

Under circumstances where the operating frequency of the CPU 110 tendsto shift toward high frequencies, it could be assumed that the CPU 110is operated at approximately 1 GHz. In such a high operating frequencyrange, the electric element 100 functions as a noise filter forconfining the unwanted high-frequency current, which is produced by theCPU 110 operating at the high operating frequency, within the vicinityof the CPU 110 under the condition that impedance of the electricelement 100 is determined mainly by the effective inductance L that isreduced as discussed above.

FIG. 12 illustrates frequency-dependent attenuation characteristics S₂₁in the electric element 100 shown in FIG. 1. In FIG. 12, the horizontalaxis indicates frequencies, while the vertical axis indicates theattenuation characteristics S₂₁. The attenuation characteristics S₂₁shown in FIG. 12 were obtained from a simulation with an electricelement having five conductive plates connected to the side anodeelectrodes 10A, 10B and six conductive plates connected to the sidecathode electrodes 20A, 20B, 20C, 20D. For information, the attenuationcharacteristics S₂₁ indicate how much the high-frequency currents, whichwere input from the CPU 110 to the electric element 100, attenuate inthe electric element 100, on condition that the CPU 110 is set as aninput side and the power source 90 is set as an output side.

Referring to FIG. 12, the attenuation characteristics S₂₁ decline withthe frequency rise. At the frequency of 1000 MHz (1 GHz), thehigh-frequency current is attenuated to −150 dB or less. In short, theattenuation increases with an increase in frequency in the electricelement 100. Even if the frequency reaches 100 MHz or higher, theattenuation does not shrink, but becomes further greater as thefrequency rises.

Thus, as the operating frequency of the CPU 110 shown in FIG. 11 becomeshigher, the impedance of the electric element 100 is reduced inconjunction with the decrease of the effective inductance L, andtherefore the electric element 100 can improve its function as a noisefilter for confining the unwanted high-frequency current produced by theCPU 110 within the vicinity of the CPU 110.

FIG. 13 is a view illustrating the frequency dependence of impedance inthe electric element 100 shown in FIG. 1. In FIG. 13, the horizontalaxis indicates frequency, while the vertical axis indicates impedance.For information, the impedance in FIG. 13 was obtained, using anelectric element 100 with four terminals (two anodes and two cathodes),by converting from the attenuation characteristics S₂₁ with thefollowing expression:

$\begin{matrix}\left. \begin{matrix}{\lbrack S\rbrack = {\frac{1}{{2\hat{Z}} + 1}\begin{bmatrix}{- 1} & {2\hat{Z}} \\{2\hat{Z}} & {- 1}\end{bmatrix}}} \\{\hat{Z} = \frac{Z_{s}}{Z_{o}}}\end{matrix} \right\} & (5)\end{matrix}$In this expression, Z₀ represents characteristic impedance.

Referring to FIG. 13, the impedance declines with an increase infrequency. At the frequency of several hundreds of megahertz or higher,the impedance is reduced to 10⁻³(Ω) or lower. The impedance reaches 10⁻⁶(Ω) or lower at the frequency of 1000 MHz (1 GHz).

Conventional noise filters do not permit the impedance to reach 10⁻³(Ω)or lower at the frequency of hundreds of megahertz or higher, however,the electric element 100 of this invention enables the impedance to besignificantly lower than 10⁻³ (Ω) in a frequency range of severalhundreds megahertz or higher.

FIG. 14 is another view illustrating the frequency dependence ofimpedance in the electric element 100 shown in FIG. 1. In FIG. 14, thehorizontal axis indicates frequency, while the vertical axis indicatesimpedance. The impedance shown in FIG. 14 was obtained from simulationswith electric elements with one conductive plate for an anode and oneconductive plate for a cathode and indicates how the variation of theratio between a length and width of the anode conductive plateinfluences the characteristics of the element. The inductance componentis great, and a self-resonant frequency appears on the order of 100 MHz.

The impedance shown in FIG. 13 was obtained from the simulation with theelectric element having five conductive plates for an anode and sixconductive plates for a cathode, and length L1 and width W1 ofconductive plates measure 15 mm by 13 mm. Because of this configuration,the effective inductance of the electric element is reduced with anincrease of the mutual inductance, and therefore the impedance shown inFIG. 13 declines.

In FIG. 14, the simulations for the impedances were performed usingelectric elements each having various sized anode conductive plates. Theconductive plates are formed so as to have length L2, shown in FIG. 3,fixed to 10 mm and width W2 changed variously. The curves k1 to k5indicate the impedances of the electric elements with width W2 of 4 mm,6 mm, 8 mm, 10 mm and 12 mm, respectively.

As apparent from the results shown in FIG. 14, the impedances decline inall frequency ranges for the electric elements with the fixed length L2and differently widened widths W2. The impedances indicated by thecurves k4 and k5 both having W2≧L2 are reduced to 0.3Ω or lower in ahigh-frequency range of 0.2 GHz or higher.

In the present invention, length L2 and width W2 of the overlap part 20are set so as to be W2≧L2. The value of W2/L2 is set relatively large asthe operating frequency of the CPU 110 relatively rises. This reducesthe impedance of the electric element 100 in the high-frequency range.

FIG. 15 is yet another view illustrating the frequency dependence of theimpedance in the electric element 100 shown in FIG. 1. In FIG. 15, thehorizontal axis indicates frequency, while the vertical axis indicatesimpedance. For information, the impedances in FIG. 15 were obtained,using an electric element 100 with four terminals (two anodes and twocathodes), by converting from the attenuation characteristics S₂₁ withexpression (5). The curves k6 to k8 are experimental results indicatingthe frequency dependence of impedance (Z₂₁) in the electric element 100when L2>W2. Specifically, curves k6, k7 and k8 show the frequencydependence of impedance (Z₂₁) in electric elements 100 with L2=12 mm andW2=10 mm, L2=12 mm and W2=8 mm, and L2=12 mm and W2=5 mm, respectively.

As apparent from the results shown in FIG. 15, the impedance (Z₂₁) ofthe electric element 100 declines in a frequency range of 10⁷ (Hz) orhigher as length L2 becomes longer than width W2. In other words, thelonger length L2 is than width W2, the more the electric element 100,used in the operating state shown in FIG. 11, improves its noise filterfunction. When the electric element 100 is used as a noise filter, therelation of length L2 and width W2 are thus set so as to hold L2>W2.

FIG. 16 is yet another view illustrating the frequency dependence ofimpedance in the electric element 100 shown in FIG. 1. In FIG. 16, thehorizontal axis indicates frequency, while the vertical axis indicatesimpedance. For information, the impedances in FIG. 16 were obtained,using electric elements 100 with four terminals (two anodes and twocathodes), by converting from reflection characteristics S₂₂ withexpression (5).

Curve k9 shows the frequency dependence of impedance (Z₂₂) of anelectric element 100 with W2≧L2. Curve k10 shows the frequencydependence of impedance (Z₂₂) of an electric element 100 with L2>W2.

Referring to FIG. 16, the impedances (Z₂₂) of the electric elements 100show almost the same result in the frequency range of 4×10⁶ (Hz) orlower even if the relation between length L2 and width W2 is set eitherW2≧L2 or L2≧W2. On the other hand, the impedances (Z₂₂) of the electricelements 100 are reduced in the frequency range of 4×10⁶ (Hz) or higherby setting the relation between length L2 and width W2 to be W2≧L2. Bysetting length L2 and width W2 so as to be W2≧L2, the electric element100 used in the operating state shown in FIG. 11 reflects less electriccurrents fed from the CPU 110. Accordingly, when the electric element100 is used as a capacitor, the relation of length L2 and width W2 isthus set to hold W2≧L2.

The electric element 101 shown in FIG. 10 is also used in the operatingstate shown in FIG. 11 and has the same frequency dependence of theimpedance shown in FIGS. 15 and 16.

As discussed above, the electric element 100 (101) is connected betweenthe power source 90 and CPU 110, and functions as a noise filter forconfining the unwanted high-frequency current produced by the CPU 110within the vicinity of the CPU 110 or as a capacitor for supplying thepower source current to the CPU 110. When the electric element 100 isconnected between the power source 90 and CPU 110, the conductive plates11, 12, 21 to 23 are connected as transmission lines. In other words,the capacitor made up of the conductive plates 11, 12 connected to theanode electrodes 10C, 10D and the conductive plates 21 to 23 connectedto the cathode electrodes 20E, 20F does not require terminals to beconnected to the transmission line but using the conductive plates 11,12, 21 to 23 as a part of the transmission lines. The conductive plates11, 12, therefore, are conductors used for allowing the DC current Ioutput from the power source 90 to flow from the power source 90 side tothe CPU 110 side, while the conductive plates 21 to 23 are conductorsused for allowing the return current Ir to flow from the CPU 110 side tothe power source 90 side.

Consequently, the equivalent series inductance can be reduced to aminimum.

In addition, the electric element 100 (101) is so configured that acurrent flowing in the conductive plates 11, 12 connected to the anodeelectrodes 10C, 10D, (120, 130) is directed opposite to a currentflowing in the conductive plates 21 to 23 connected to the cathodeelectrodes 20E, 20F, thereby creating magnetic interference between theconductive plates 11, 12 and conductive plates 21 to 23. Because of themagnetic interference, the mutual inductance between the conductiveplates 11, 12 and conductive plates 21 to 23 reduces the self-inductanceof the conductive plates 11, 12. The reduction of the self-inductance ofthe conductive plates 11, 12 reduces the effective inductance of theelectric element 100 (101), thus lowering the impedance of the electricelement 100 (101).

The first characteristic feature of this invention discussed above isthat the conductive plates 11, 12, 21 to 23, which constitute electrodesof the capacitor, are connected as a part of the transmission lines. Thesecond characteristic feature is that the current flowing through theconductive plates 11, 12 connected to the anode electrodes 10C, 10D andthe current flowing in the opposite direction through the conductiveplates 21 to 23 connected to the cathode electrodes 20E, 20F createmagnetic interference between the conductive plates 11, 12 andconductive plates 21 to 23, thereby making the effective inductance ofthe conductive plates 11, 12 smaller than the self-inductance of theconductive plates 11, 12, therefore lowering the impedance of theelectric element 100 (101). The third characteristic feature is thateach of the conductive plates 11, 12 passing the DC current constitutingan electric current from the power source is sandwiched by twoconductive plates (conductive plates 21 and 22 or conductive plates 22and 23) connected to ground potential.

The second characteristic feature is realized by adopting the structurein which the return current Ir from the CPU 110 flows to the conductiveplates 21 to 23 placed in the electric element 100 (101).

The equivalent series inductance can be reduced to a minimum accordingto the first characteristic feature, and the unwanted high-frequencycurrent can be confined in the vicinity of the CPU 110 according to thesecond characteristic feature. The third characteristic feature preventsnoise generated by the electric element 100 (101) from leaking outsideas well as preventing noise generated outside the electric element 100(101) from affecting the electric element 100 (101).

Although all the dielectric layers 1 to 5 are composed of the samedielectric material (BaTiO₃) in the above embodiment, the presentinvention is not limited to this. The dielectric layers 1 to 5 can becomposed of different dielectric materials on an individual basis.Alternatively, the dielectric layers 1 to 5 can be put into two groupseach composed of the same material, but the materials are different toeach other. Typically the dielectric layers 1 to 5 may be composed ofone or more kinds of dielectric materials. Any dielectric material forforming the dielectric layers 1 to 5 preferably has the relativepermittivities of 3000 or more.

In addition to BaTiO₃, the dielectric layers may be composed of Ba(Ti,Sn)O₃, Bi₄Ti₃O₁₂, (Ba, Sr, Ca)TiO₃, (Ba, Ca)(Zr, Ti)O₃, (Ba, Sr, Ca)(Zr,Ti)O₃, SrTiO₃, CaTiO₃, PbTiO₃, Pb(Zn, Nb)O₃, Pb(Fe, W)O₃, Pb(Fe, Nb)O₃,Pb(Mg, Nb)O₃, Pb(Ni, W)O₃, Pb(Mg, W)O₃, Pb(Zr, Ti)O₃, Pb(Li, Fe, W)O₃,Pb₅Ge₃O₁₁ and CaZrO₃, and so forth.

Although the anode electrodes 10C, 10D (120, 130), side anode electrodes10A, 10B, conductive plates 11, 12, 21 to 23, side cathode electrodes20A, 20B, 20C, 20D and cathode electrodes 20E, 20F are composed ofnickel (Ni) in the above embodiment, the present invention is notlimited to this. The anode electrodes 10C, 10D, (120, 130), side anodeelectrodes 10A, 10B, conductive plates 11, 12, 21 to 23, side cathodeelectrodes 20A, 20B, 20C, 20D and cathode electrodes 20E, 20F can becomposed of any of silver (Ag), palladium (Pd), silver-palladium alloy(Ag—Pd), platinum (Pt), gold (Au), copper (Cu), rubidium (Ru) andtungsten (W).

Although the electric element 100 (101) comprises the dielectric layers1 to 5 in the above embodiment, the present invention is not limited tothis. The electric element 100 (101) does not need to comprise thedielectric layers 1 to 5. Since magnetic interference could occurbetween the conductive plates 11, 12 and conductive plates 21 to 23 evenwithout the dielectric layers 1 to 5, the aforementioned mechanism canreduce the impedance of the electric element 100 (101).

Although the number of the conductive plates to be connected to theanode electrodes 10C, 10D (120, 130) is two (i.e. conductive plates 11,12), while the number of the conductive plates to be connected to thecathode electrodes 20E, 20F is three (i.e. conductive plates 21, 22, 23)in the above embodiment, the present invention is not limited to this.The electric element 100 (101) can comprise n-number (n is a positiveinteger) of the conductive plates connected to the anode electrodes 10C,10D (120, 130) and m-number (m is a positive integer) of the conductiveplates connected to the cathode electrodes 20E, 20F. In this case, theelectric element 100 (101) comprises j-number (j=m+n) of the dielectriclayers. The magnetic interference to make the effective inductance smallcan be generated as long as there are at least one conductive plateconnected to the anode electrodes 10C, 10D, (120, 130) and at least oneconductive plate connected to the cathode electrodes 20E, 20F.

In the present invention, the number of the conductive plates connectedto the anode electrodes 10C, 10D (120, 130) and the number of theconductive plates connected to the cathode electrodes 20E, 20F areincreased with an increase of the electric current flowing in theelectric element 100 (101). Since the conductive plates connected to theanode electrodes 10C, 10D (120, 130) and the conductive plates connectedto the cathode electrodes 20E, 20F are connected between two anodeelectrodes (i.e. 10C and 10D or 120 and 130), or between two cathodeelectrodes (i.e. 20E and 20F) in parallel, the addition of theconductive plates connected to the anode electrodes 10C, 10D (120, 130)and the conductive plates connected to the cathode electrodes 20E, 20Fcan increase the amount of electric current flowing in the electricelement 100 (101).

In order to relatively reduce impedance of the electric element 100(101), the number of the conductive plates connected to the anodeelectrodes 10C, 10D (120, 130) and the number of the conductive platesconnected to the cathode electrodes 20E, 20F are increased in thepresent invention. Because the addition of the conductive platesconnected to the anode electrodes 10C, 10D (120, 130) and the conductiveplates connected to the cathode electrodes 20E, 20F provides additionalcapacitors to be connected in parallel, thereby increasing the effectivecapacitance of the electric element 100 (101), therefore lowering theimpedance.

Although the conductive plates 11, 12 are disposed parallel with theconductive plates 21 to 23 in the above embodiment, the presentinvention is not limited to this. The conductive plates 11, 12, 21 to 23can be disposed so that the distance between the conductive plates 11,12 and the conductive plates 21 to 23 varies along the longitudinaldirection DR1.

Although the electric element 100 (101) is connected to the CPU 110 inthe above embodiment, the present invention is not limited to this. Theelectric element 100 (101) can be connected to any electrical loadcircuit as long as the electrical load circuit operates at apredetermined frequency.

Although the electric element 100 (101) is used as a noise filter forconfining the unwanted high-frequency current produced by the CPU 110within the vicinity of the CPU 110 in the above embodiment, the presentinvention is not limited to this. Since the electric element 100 (101)includes four capacitors connected in parallel as discussed above, theelectric element 100 (101) also can be used as a capacitor.

More concretely, the electric element 100 (101) can be used in notebookcomputers, CD-RW/DVD recorders and players, game machines, informationappliances, digital cameras, in-vehicle electric equipment, in-vehicledigital equipment, MPU peripheral circuitry and DC/DC converters and soforth.

Electric elements that are adopted in notebook computers and CD-RW/DVDrecorders and players as a capacitor, but function as a noise filter,arranged between the power source 90 and CPU 110, for confining theunwanted high-frequency current produced by the CPU 110 within thevicinity of the CPU 110 are grouped with the electric element 100 (101)of the present invention.

According to the above-described first embodiment, the electric element100 comprises conductive plates 11, 12, conductive plates 21 to 23alternately disposed with the conductive plates 11, 12, a side anodeelectrode 10A and an anode electrode 10C connected to one end of theconductive plates 11, 12, a side anode electrode 10B and an anodeelectrode 10D connected to the other end of the conductive plates 11,12, side cathode electrodes 20A, 20B and a cathode electrode 20Econnected to the conductive plates 21 to 23 in the proximity of one endof the conductive plates 21 to 23, and side cathode electrodes 20C, 20Dand a cathode electrode 20F connected to the conductive plates 21 to 23in the proximity of the other end of the conductive plates 21 to 23. Theelectric current flows in order from the anode electrode 10C, side anodeelectrode 10A, conductive plates 11, 12, side anode electrode 10B toanode electrode 10D, while the return current flows in order from thecathode electrode 20F, side cathode electrodes 20C, 20D, conductiveplates 21 to 23, side cathode electrodes 20A, 20B to cathode electrode20E. With this configuration, the return current flowing in theconductive plates 21 to 23 causes mutual inductance between theconductive plates 11, 12 and conductive plates 21 to 23, thereby makingthe effective inductance of the conductive plates 11, 12 smaller thanthe self-inductance of the conductive plates 11, 12.

The electric element 101 comprises conductive plates 11, 12, conductiveplates 21, 22 alternately disposed with the conductive plates 11, 12, ananode electrode 120 connected to one end of the conductive plates 11,12, an anode electrode 130 connected to the other end of the conductiveplates 11, 12, a side cathode electrodes 20A, 20B and a cathodeelectrode 20E connected to the conductive plates 21, 22 in the proximityof one end of the conductive plates 21, 22, and side cathode electrodes20C, 20D and a cathode electrode 20F connected to the conductive plates21, 22 in the proximity of the other end of the conductive plates 21,22. The electric current flows in order from the anode electrode 120,through the conductive plates 11, 12, to the anode electrode 130, whilethe return current flows in order from the cathode electrode 20F,through the side cathode electrodes 20C, 20D, conductive plates 21, 22,side cathode electrodes 20A, 20B to the cathode electrode 20E. With thisconfiguration, the return current flowing in the conductive plates 21,22 causes mutual inductance between the conductive plates 11, 12 andconductive plates 21, 22, thereby making the effective inductance of theconductive plates 11, 12 smaller than the self-inductance of theconductive plates 11, 12.

According to the present invention, the impedance can be reduced withthe decrease of the inductance.

The Second Embodiment

FIG. 17 is a schematic view illustrating the structure of an electricelement according to the second embodiment. Referring to FIG. 17, theelectric element 200 of the second embodiment includes conductive plates201, 202 instead of the conductive plates 21, 22 of the electric element101 shown in FIG. 10 and the same components as those of the electricelement 101.

The conductive plates 201, 202 are composed of nickel (Ni). Theconductive plate 201 is placed on a principal surface of a dielectriclayer 1, while the conductive plate 202 is placed on a principal surfaceof a dielectric layer 3. The conductive plates 201, 202 are connected toside cathode electrodes 20A, 20C on the front face 100D of the electricelement 200 and side cathode electrodes 20B, 20D on the rear face 100E.

FIGS. 18A to 18E are plan views of the dielectric layers 1, 2 andconductive plates 11, 201 shown in FIG. 17 and a bottom view of theelectric element 200. FIG. 18A is a plan view of the dielectric layer 1,FIG. 18B is a plan view of the conductive plate 11, FIG. 18C is a planview of the dielectric layer 2, FIG. 18D is a plan view of theconductive plate 201, and FIG. 18E is a bottom view of the electricelement 200.

The dielectric layers 1, 2 have length L1 and width W1 (see FIGS. 18Aand 18C) as discussed above. The conductive plate 11 has length L1 andwidth W2 (see FIG. 18B) as discussed above. The dielectric layers 3 to 5are in the same form of a flat plate as the dielectric layers 1, 2,while the conductive plate 12 is in the same form of a flat plate as theconductive plate 11.

The conductive plate 201 has length L2 and width W2. Length L2 isshorter than length L1, and width W2 is narrower than width W1. Theconductive plate 201 has extending portions 201A, 201B, 201C, 201D. Theextending portions 201A, 201B are located closer to one side 201E thanthe midpoint of the conductive plate 201 in the longitudinal direction,while the extending portions 201C, 201D are located closer to the otherside 201F than the midpoint of the conductive plate 201 in thelongitudinal direction. The provision of the extending portions 201A,201B, 201C, 201D widens the width from the extending portion 201A to201B and from the extending portion 201C to 201D of the conductive plate201 to width W1. This configuration allows the extending portions 201A,201B, 201C, 201D to be connected to the side cathode electrodes 20A,20B, 20C, 20D, respectively. The conductive plate 202 shown in FIG. 17is in the same form of a flat plate as the conductive plate 201 shown inFIG. 18D.

On the bottom face of the electric element 200, an anode electrode 120(strip electrode 122) is disposed on one side of the electric element200, while an anode electrode 130 (strip electrode 132) is disposed onthe other side of the electric element 200. A cathode electrode 20E isdisposed between the anode electrode 120 and 130 but closer to the anodeelectrode 120 than the midpoint between the anode electrodes 120 and130, while a cathode electrode 20F is disposed between the anodeelectrodes 120 and 130 but closer to the anode electrode 130 than themidpoint between the anode electrode 120 and anode electrode 130 (seeFIG. 18E).

Due to such plane shapes of the conductive plates 11, 12, 201, 202 andthe dielectric layers 1 to 5 as shown in FIGS. 18A to 18E, in theelectric element 200, the anode electrode 120 is connected to theconductive plates 11, 12 on the side face 100A of the electric element200, the anode electrode 130 is connected to the conductive plates 11,12 on the side face 100B, opposite to the side face 100A, of theelectric element 200, the side cathode electrodes 20A, 20C are connectedto the conductive plates 201, 202 on the front face 100D, approximatelyperpendicular to the side faces 100A, 100B, of the electric element 200,and the side cathode electrodes 20B, 20D are connected to the conductiveplates 201, 202 on the rear face 100E, approximately perpendicular tothe side faces 100A, 100B, of the electric element 200.

The electric element 200 shown in FIG. 17 has the frequency dependenceof the impedance shown in the aforementioned FIGS. 15 and 16. Therefore,when the electric element 200 is used as a noise filter, the relation oflength L2 and width W2 is set to be L2>W2. When the electric element 200is used as a capacitor, the relation of length L2 and width W2 is set tobe W2≧L2.

As to the other structure, the electric element 200 is the same as theelectric element of the first embodiment.

The Third Embodiment

FIG. 19 is a schematic view illustrating the structure of an electricelement according to the third embodiment. Referring to FIG. 19, theelectric element 300 of the third embodiment includes conductive plates301, 302 instead of the conductive plates 11, 12 of the electric element101 shown in FIG. 10, conductive plates 311, 312 instead of theconductive plates 21, 22, an anode electrode 320 instead of the sideanode electrode 10A and anode electrode 10C, an anode electrode 330instead of the side anode electrode 10B and anode electrode 10D, acathode electrode 340 instead of the side cathode electrodes 20A, 20Band cathode electrode 20E, a cathode electrode 350 instead of the sidecathode electrodes 20C, 20D and cathode electrode 20F. The othercomponents are the same as those of the electric element 101.

The conductive plate 301 is placed on a principal surface of thedielectric layer 2, while the conductive plate 302 is placed on aprincipal surface of the dielectric layer 4. The conductive plate 311 isplaced on a principal surface of the dielectric layer 1, while theconductive plate 312 is placed on a principal surface of the dielectriclayer 3. These conductive plates 301, 302, 311, 312 are composed ofnickel (Ni).

The anode electrode 320 is disposed on a part of the side face 100A,bottom face 100C, rear face 100E and top face 100F of the electricelement 300, and connected to one end of the conductive plates 301, 302.More specifically, the anode electrode 320 includes a side anodeelectrode 321 and strip electrodes 322 to 324. The side anode electrode321 is arranged on the side face 100A of the electric element 300 andconnected to one end of the conductive plates 301, 302. The stripelectrodes 322, 323, 324 are arranged on the bottom face 100C, rear face100E, top face 100F, respectively, of the electric element 300.

The anode electrode 330 is disposed on a part of the side face 100B,bottom face 100C, front face 100D and top face 100F of the electricelement 300, and connected to the other end of the conductive plates301, 302. More specifically, the anode electrode 330 includes a sideanode electrode 331 and strip electrodes 332 to 334. The side anodeelectrode 331 is arranged on the side face 100B of the electric element300 and connected to the other end of the conductive plates 301, 302.The strip electrodes 332, 333, 334 are arranged on the bottom face 100C,front face 100D, top face 100F, respectively, of the electric element300.

The cathode electrode 340 is disposed on a part of the side face 100A,bottom face 100C, front face 100D and top face 100F of the electricelement 300, and connected to one end of the conductive plates 311, 312.More specifically, the cathode electrode 340 includes a side cathodeelectrode 341 and strip electrodes 342 to 344. The side cathodeelectrode 341 is arranged on the side face 100A of the electric element300 and connected to one end of the conductive plates 311, 312. Thestrip electrodes 342, 343, 344 are arranged on the bottom face 100C,front face 100D, top face 100F, respectively, of the electric element300.

The cathode electrode 350 is disposed on a part of the side face 100B,bottom face 100C, rear face 100E and top face 100F of the electricelement 300, and connected to the other end of the conductive plates311, 312. More specifically, the cathode electrode 350 includes a sidecathode electrode 351 and strip electrodes 352 to 354. The side cathodeelectrode 351 is arranged on the side face 100B of the electric element300 and connected to the other end of the conductive plates 311, 312.The strip electrodes 352, 353, 354 are disposed on the bottom face 100C,rear face 100E, top face 100F, respectively, of the electric element300.

FIGS. 20A to 20E are plan views of the dielectric layers 1, 2 andconductive plates 301, 311 shown in FIG. 19 and a bottom view of theelectric element 300 shown in FIG. 19. FIG. 20A is a plan view of thedielectric layer 1, FIG. 20B is a plan view of the conductive plate 301,FIG. 20C is a plan view of the dielectric layer 2, FIG. 20D is a planview of the conductive plate 311, and FIG. 20E is a bottom view of theelectric element 300.

The dielectric layers 1, 2 have the aforementioned length L1 and widthW1 (see FIGS. 20A, 20C). The dielectric layers 3 to 5 have the sameshape and dimensions as the dielectric layers 1, 2.

The conductive plate 301 has an approximately rectangular plane. Theconductive plate 301 has length L2 along in a lateral direction of therectangle and width W2 in a vertical direction of the rectangle. LengthL2 is shorter than length L1, while width W2 is narrower than width W1.In addition, the conductive plate 301 has two extending portions 301A,301B. The two extending portions 301A, 301B are provided at oppositeends on one of two diagonal lines of the rectangle (see FIG. 20B). Thisconfiguration allows the extending portions 301A and 301B to beconnected to the side anode electrode 321 of the anode electrode 320 andthe side anode electrode 331 of the anode electrode 330, respectively.The conductive plate 302 has the same shape and dimensions as theconductive plate 301.

The conductive plate 311 has an approximately rectangular plane. Theconductive plate 311 has length L2 in a lateral direction of therectangle and width W2 in a vertical direction of the rectangle. Inaddition, the conductive plate 311 has two extending portions 311A,311B. The two extending portions 311A, 311B are provided at oppositeends on the other diagonal line of the two diagonal lines of therectangle (see FIG. 20D). This configuration allows the extendingportions 311A and 311B to be connected to the side cathode electrode 341of the cathode electrode 340 and the side cathode electrode 351 of thecathode electrode 350, respectively. The conductive plate 312 has thesame shape and dimensions as the conductive plate 311.

The anode electrode 320 (strip electrode 322), anode electrode 330(strip electrode 322), cathode electrode 340 (strip electrode 342) andcathode electrode 350 (strip electrode 352) are located in four corners,respectively, of the bottom face 100C of the electric element 300. Thetwo anode electrodes 320, 330 are disposed at the opposite ends on oneof the two diagonal lines of the rectangle, while the two cathodeelectrodes 340, 350 are disposed at the opposite ends on the otherdiagonal line of the two diagonal lines of the rectangle (see FIG. 20E).

Due to such plane shapes of the conductive plates 301, 302, 311, 312 anddielectric layers 1 to 5 as shown in FIGS. 20A to 20E, in the electricelement 300, the anode electrode 320 is connected to the conductiveplates 301, 302 on the side face 100A of the electric element 300, whilethe anode electrode 330 is connected to the conductive plates 301, 302on the side face 100B, opposite to the side face 100A, of the electricelement 300. The cathode electrode 340 is connected to the conductiveplates 311, 312 on the side face 100A of the electric element 300, whilethe cathode electrode 350 is connected to the conductive plates 311, 312on the side face 100B of the electric element 300.

The electric element 300 shown in FIG. 19 has the frequency dependenceof the impedance shown in aforementioned FIGS. 15 and 16. Therefore,when the electric element 300 is used as a noise filter, the relation oflength L2 and width W2 is set so as to be L2>W2. When the electricelement 300 is used as a capacitor, the relation of length L2 and widthW2 is set so as to be W2≧L2.

As to the other structure, the electric element 300 is the same as theelectric element of the first embodiment.

The Fourth Embodiment

FIG. 21 is a schematic view illustrating the structure of an electricelement according to the fourth embodiment. Referring to FIG. 21, theelectric element 400 of the fourth embodiment includes conductive plates401, 402 instead of the conductive plates 11, 12 of the electric element101 shown in FIG. 10, conductive plates 411, 412 instead of theconductive plates 21, 22, an anode electrode 420 instead of the sideanode electrode 10A and anode electrode 10C, an anode electrode 430instead of the side anode electrode 10B and anode electrode 10D, acathode electrode 440 instead of the side cathode electrodes 20A, 20Band cathode electrode 20E, a cathode electrode 450 instead of the sidecathode electrodes 20C, 20D and cathode electrode 20F. The othercomponents are the same as those of the electric element 101.

The conductive plate 401 is placed on a principal surface of thedielectric layer 2, while the conductive plate 402 is placed on aprincipal surface of the dielectric layer 4. The conductive plate 411 isplaced on a principal surface of the dielectric layer 1, while theconductive plate 412 is placed on a principal surface of the dielectriclayer 3. These conductive plates 401, 402, 411, 412 are composed ofnickel (Ni).

The anode electrode 420 is disposed on the front face 100D, bottom face100C and top face 100F of the electric element 400 and connected to theconductive plates 401, 402 in the proximity of one end of the conductiveplates 401, 402. The anode electrode 430 is disposed on the front face100D, bottom face 100C and top face 100F of the electric element 400 andconnected to the conductive plates 401, 402 in the proximity of theother end of the conductive plates 401, 402.

The cathode electrode 440 is disposed on the rear face 100E, bottom face100C and top face 100F of the electric element 400 and connected to theconductive plates 411, 412 in the proximity of one end of the conductiveplates 411, 412. The cathode electrode 450 is disposed on the rear face100E, bottom face 100C and top face 100F of the electric element 400 andconnected to the conductive plates 411, 412 in the proximity of theother end of the conductive plates 411, 412.

FIGS. 22A to 22E are plan views of the dielectric layers 1, 2 andconductive plates 401, 411 shown in FIG. 21 and a bottom view of theelectric element 400 shown in FIG. 21. FIG. 22A is a plan view of thedielectric layer 1, FIG. 22B is a plan view of the conductive plate 401,FIG. 22C is a plan view of the dielectric layer 2, FIG. 22D is a planview of the conductive plate 411, and FIG. 22E is a bottom view of theelectric element 400.

The dielectric layers 1, 2 have the aforementioned length L1 and widthW1 (see FIGS. 22A, 22C). The dielectric layers 3 to 5 have the sameshape and dimensions as the dielectric layers 1, 2.

The conductive plate 401 has an approximately rectangular plane. Theconductive plate 401 has length L2 in a lateral direction of therectangle and width W2 in a vertical direction of the rectangle. LengthL2 is shorter than length L1, while width W2 is narrower than width W1.In addition, the conductive plate 401 includes two extending portions401A, 401B. The two extending portions 401A, 401B are provided on one oftwo sides in the lateral direction of the rectangle. In other words, thetwo extending portions 401A, 401B are formed on the same side (see FIG.22B). This configuration allows the extending portions 401A, 401B to beconnected to the anode electrodes 420, 430, respectively. The conductiveplate 402 has the same shape and dimensions as the conductive plate 401.

The conductive plate 411 has an approximately rectangular plane. Theconductive plate 411 has length L2 in a lateral direction of therectangle and width W2 in a vertical direction of the rectangle. Inaddition, the conductive plate 411 has two extending portions 411A,411B. The two extending portions 411A, 411B are provided on the otherside of two sides along the lateral direction of the rectangle. In otherwords, the two extending portions 411A, 411B are provided on the sideopposite to the side provided with two extending portions 401A, 401B ofthe conductive plate 401 (see FIG. 22D). This configuration allows theextending portions 411A, 411B to be connected to the cathode electrodes440, 450, respectively. The conductive plate 412 has the same shape anddimensions as the conductive plate 411.

The anode electrode 420, anode electrode 430, cathode electrode 440 andcathode electrode 450 are arranged separately near four corners,respectively, on the bottom face 100C of the electric element 400. Thetwo anode electrodes 420, 430 are located along one side out of twosides of the rectangle, while the two cathode electrodes 440, 450 arelocated along the other side out of two sides of the rectangle (see FIG.22E).

Due to such plane shapes of the conductive plates 401, 402, 411, 412 anddielectric layers 1 to 5 as shown in FIGS. 22A to 22E, in the electricelement 400, the anode electrodes 420, 430 are connected to theconductive plates 401, 402 on the front face 100D of the electricelement 400, while the cathode electrodes 440, 450 are connected to theconductive plates 411, 412 on the rear face 100E of the electric element400.

The electric element 400 shown in FIG. 21 has the frequency dependenceof the impedance shown in aforementioned FIGS. 15 and 16. Therefore,when the electric element 400 is used as a noise filter, the relation ofthe length L2 and width W2 is set so as to be L2>W2. When the electricelement 400 is used as a capacitor, the relation of the length L2 andwidth W2 is set so as to be W2≧L2.

As to the other structure, the electric element 400 is the same as theelectric element of the first embodiment.

Exemplary Modifications

FIG. 23 is a schematic view illustrating the first modification of theelectric element according to the embodiments of the present invention.Referring to FIG. 23, the electric element 500 comprises conductivewires 501 to 503, 511, 512, anode electrodes 504, 505, and cathodeelectrodes 513, 514.

The conductive wires 501 to 503 are connected approximately parallelbetween the anode electrodes 504, 505. The conductive wires 511, 512 areconnected approximately parallel between the cathode electrodes 513,514. The conductive wire 511 is located between the conductive wires501, 502, while the conductive wire 512 is located between theconductive wires 502, 503. Consequently, the conductive wires 501 to503, 511, 512 are disposed approximately parallel in one plane.

FIG. 24 is a plan view illustrating the electric element 500 shown inFIG. 23. Referring to FIG. 24, the conductive wires 501 to 503 havelength L3, and the conductive wires 511, 512 have length L4. Length L3may be 15 mm, and length L4 may be 10 mm, for example.

The space between the conductive wire 501 and conductive wire 511 is setat d1. The space d1 may be several hundreds of micrometers, for example.The spaces between the conductive wire 511 and conductive wire 502,between the conductive wire 502 and conductive wire 512, and between theconductive wire 503 and conductive wire 512 are also set at d1.

A DC current flows through the conductive wires 501 to 503 in thedirection of arrow 506, while flowing through the conductive wires 511,512 in the direction of arrow 507. The self-inductance of the conductivewires 501 to 503 is reduced by the mutual inductance occurring betweenthe conductive wires 501 to 503 and conductive wire 511 or 512, therebymaking the effective inductance smaller than the self-inductance. As aresult, the impedance of the electric element 500 is lowered.

FIG. 25 is a schematic view illustrating the second modification of theelectric element according to the embodiment of the present invention.Referring to FIG. 25, the electric element 600 comprises conductivewires 601 to 603, 611 to 613, anode electrodes 604, 605, and cathodeelectrodes 614, 615.

The conductive wires 601 to 603 are connected approximately parallelbetween the anode electrodes 604 and 605. The conductive wires 611 to613 are connected approximately parallel between the cathode electrodes614 and 615.

FIGS. 26A and 26B are side views illustrating the electric element 600shown in FIG. 25. FIG. 26A is a side view of the electric element 600viewed from direction A in FIG. 25, while FIG. 26B is a side view of theelectric element 600 viewed from direction B in FIG. 25. In FIG. 26B,the anode electrodes 604, 605 and cathode electrodes 614, 615 areomitted.

Referring to FIGS. 26A and 26B, each of the conductive wires 603, 613has length L3. The conductive wires 611 to 613 are opposed to theconductive wires 601 to 603, respectively. The space between conductivewires 601 to 603 and conductive wires 611 to 613 is set at d2. The spaced2 may be several hundreds of micrometers, for example.

The space between the conductive wires 601 and 602 is set at d3. Thespace d3 may be several hundreds of micrometers, for example. The spacesbetween the conductive wires 602 and 603, between the conductive wires611 and 612, and between the conductive wires 612 and 613 are also setat d3.

In the electric element 600, the conductive wires 601 to 603 connectedto the anode electrodes 604, 605 are arranged on a different plane fromthe conductive wires 611 to 613 connected to the cathode electrode 614,615.

A DC current flows through the conductive wires 601 to 603 in thedirection of arrow 606, while a DC current flows through the conductivewires 611 to 613 in the direction of arrow 607. The DC currents flowingin the opposite directions cause the mutual inductance between theconductive wires 601 to 603 and conductive wires 611 to 613, whichmaking the self-inductance of the conductive wires 601 to 603 small, andtherefore the effective inductance is reduced. As a result, theimpedance of the electric element 600 is lowered.

FIG. 27 is a schematic view illustrating the third modification of theelectric element according to the embodiments of the present invention.FIGS. 28A and 28B are a plan view and a side view, respectively,illustrating the electric element shown in FIG. 27. FIG. 28A is a planview viewed from direction C in FIG. 27, and FIG. 28B is a side viewviewed from direction B in FIG. 27.

Referring to FIGS. 27, 28A and 28B, the electric element 700 includesthe conductive wires 601 to 603 and anode electrodes 604, 605, of theelectric element 600 in FIG. 25, shifted in a direction perpendicular tothe direction of length L3. When the conductive wires 601 to 603 andconductive wires 611 to 613 are viewed in one plane, the conductivewires 601, 602 are arranged between the conductive wires 611 and 612 andbetween the conductive wires 612 and 613, respectively (see FIG. 28A).

In the electric element 700, a DC current flows in the conductive wires601 to 603 in the opposite direction to a DC current flowing in theconductive wires 611 to 613. Because the conductive wires 601, 602 arearranged between the conductive wires 611 and 612, and between theconductive wires 612 and 613, respectively, in one plane, theself-inductance of the conductive wire 601 is reduced by the mutualinductance generated between the conductive wire 601 and conductivewires 611, 612. The effective inductance of the conductive wire 602becomes lower than the self-inductance by the mutual inductancegenerated between the conductive wire 602 and conductive wires 612, 613.

As a result, the effective inductance in the electric element 700 can bereduced, and therefore the impedance is lowered.

FIG. 29 is a schematic view illustrating the fourth modification of theelectric element according to the embodiments of the present invention.FIG. 30 is a plan view of the electric element 800 viewed from directionC in FIG. 29. Referring to FIGS. 29 and 30, the electric element 800includes the conductive wires 601 to 603 and anode electrodes 604, 605of the electric element 600 in FIG. 25, rotated by a predetermined angleθ (−90 degrees≦θ≦90 degrees) within a plane parallel to a planeincluding the conductive wires 611 to 613 and cathode electrodes 614,615. The θ is a degree with respect to a direction, from the left end toright end of the conductive wires 611 to 613 in FIG. 30, which isdefined as zero degree.

In the electric element 800, a DC current flows through the conductivewires 601 to 603 in the direction of arrow 608, while a DC current flowsthrough the conductive wires 611 to 613 in the direction of arrow 607.The DC current flowing through the conductive wires 601 to 603 forms anangle 180-θ with the DC current flowing through the conductive wires 611to 613. Because the angle 180-θ is set in a range from 90 degrees to 270degrees, magnetic interference between the conductive wires 601 to 603and conductive wires 611 to 613 occurs, and therefore the magnetic fluxproduced by the DC current flowing in the conductive wires 601 to 603 isreduced by the magnetic flux produced by the DC current flowing in theconductive wires 611 to 613.

Thus, the effective inductance of the conductive wires 601 to 603 isreduced to be smaller than the self-inductance by the mutual inductancegenerated between the conductive wires 601 to 603 and conductive wires611 to 613. As a result, the smaller effective inductance of theelectric element 800 causes the impedance to be lowered.

In the present invention, the DC current flowing in the conductive wires601 to 603 and the DC current flowing in the conductive wires 611 to 613are directed so as to intersect with each other, if viewed in one plane,and therefore the magnetic flux produced by the DC current flowing inthe conductive wires 601 to 603 is reduced by the magnetic flux producedby the DC current flowing in the conductive wires 611 to 613.

The electric element 500 (600, 700, 800) connected between the powersource 90 and CPU 110, is used as a substitute for the electric element100. The anode electrode 504 (604) is connected to the lead wire 121,the anode electrode 505 (605) is connected to the lead wire 123, thecathode electrode 513 (614) is connected to the lead wire 122, and thecathode electrode 514 (615) is connected to the lead wire 124. Thecathode electrodes 513, 514 (614, 615) are connected to groundpotential.

In such the electric element 500 (600, 700, 800), a DC current from thepower source 90 flows from the anode electrode 504 (604) to the anodeelectrode 505 (605), while a return current from the CPU 110 flows fromthe cathode electrode 514 (615) to the cathode electrode 513 (614).

As a result, the effective inductance of the electric element 500 (600,700, 800) is reduced, therefore lowering the impedance. In addition, theelectric element 500 (600, 700, 800) causes an unwanted high-frequencycurrent produced by the CPU 110 to flow within circuitry made up of theelectric element and the CPU 110 to confine the unwanted high-frequencycurrent within the vicinity of the CPU 110.

The electric element 500 (600, 700, 800) may further comprisedielectrics for covering the conductive wires 501 to 503, 511 and 512(601 to 603, 611 to 613).

The electric element 500 (600, 700, 800) may comprise flat plate-likeconductors instead of the conductive wires 501 to 503, 511, 512 (601 to603, 611 to 613).

The Fifth Embodiment

FIG. 31 is a schematic view illustrating the structure of an electriccircuit according to the fifth embodiment. Referring to FIG. 31, theelectric circuit 1000 of the fifth embodiment comprises a power source90, an electric element 100, a CPU 110, and transmission lines 1120,1130, 1140, 1150.

The power source 90 includes a positive terminal 91 and a negativeterminal 92. The electric element 100 includes anode electrodes 101, 102and cathode electrodes 103, 104. The CPU 110 includes a positiveterminal 111 and a negative terminal 112.

The transmission line 1120 has one end connected to the positiveterminal 91 of the power source 90 and the other end connected to theanode electrode 101 of the electric element 100. The transmission line1130 has one end connected to the anode electrode 102 and the other endconnected to the positive terminal 111 of the CPU 110.

The transmission line 1140 has one end connected to the negativeterminal 92 of the power source 90 and the other end connected to thecathode electrode 103 of the electric element 100. The transmission line1150 has one end connected to the cathode electrode 104 of the electricelement 100 and the other end connected to the negative terminal 112 ofthe CPU 110.

In the electric circuit 1000, overlap parts 20 of conductive plates 11,12 and conductive plates 21 to 23 of the electric element 100 havelength L2 and width W2 which are set so as to hold L2>W2. The electricelement 100 functions as a noise filter.

The power source 90 supplies a DC current I from the positive terminal91 through the transmission line 1120 to the electric element 100, andreceives a return current Ir, which is fed from the electric element 100through the transmission line 1140, at the negative terminal 92.

The electric element 100 receives the DC current I, which is suppliedfrom the power source 90 via the transmission line 1120, at the anodeelectrode 101, and supplies the received DC current I from the anodeelectrode 102 through the transmission line 1130 to the CPU 110. Theelectric element 100 further receives the return current Ir, which issupplied from the CPU 110 through the transmission line 1150, at thecathode electrode 104, and supplies the received return current Ir fromthe cathode electrode 103 through the transmission line 1140 to thepower source 90. In addition, the electric element 100 confines anunwanted high-frequency current transmitted through the transmissionlines 1130, 1150 from the CPU 110 within circuitry made up of theelectric element 100, transmission lines 1130, 1150 and CPU 110 in theaforementioned manner, thereby preventing the unwanted high-frequencycurrent from leaking toward the power source 90.

The CPU 110 is driven with the DC current I supplied from the electricelement 100 and operates at a predetermined frequency. The CPU 110supplies the return current Ir through the transmission line 1150 to theelectric element 100.

In the above-described electric circuit 1000, the electric element 100supplies the DC current from the power source 90 to the CPU 110, andconfines the unwanted high-frequency current produced by the CPU 110within the circuitry made up of the electric element 100, thetransmission lines 1130, 1150 and the CPU 110, thereby preventingleakage of the unwanted high-frequency current toward the power source90.

Thus, the present invention can prevent the unwanted high-frequencycurrent from leaking toward the power source.

In the fifth embodiment, any one of the electric elements 101, 200, 300,400, 500, 600, 700 and 800 can be used instead of the electric element100.

The Sixth Embodiment

FIG. 32 is a schematic view illustrating the structure of an electriccircuit according to the sixth embodiment. Referring to FIG. 32, theelectric circuit 1100 of the sixth embodiment comprises a capacitor 160and transmission lines 1170, 1180 in addition to the components of theelectric circuit 1000 shown in FIG. 31. The other components are thesame as these of the electric circuit 1000.

The capacitor 160 includes an anode electrode 161 and a cathodeelectrode 162. In the electric circuit 1100, the transmission line 1130has the other end connected to the anode electrode 161 of the capacitor160. The transmission line 1150 has the other end connected to thecathode electrode 162 of the capacitor 160.

The transmission line 1170 has one end connected to the anode electrode161 of the capacitor 160 and the other end connected to the positiveterminal 111 of the CPU 110. The transmission line 1180 has one endconnected to the cathode electrode 162 of the capacitor 160 and theother end connected to the negative terminal 112 of the CPU 110.

In the electric circuit 1100, overlap parts 20 of the conductive plates11, 12 and conductive plates 21 to 23 of the electric element 100 havelength L2 and width W2 which are set so as to hold L2>W2. The electricelement 100 functions as a noise filter.

The power source 90 supplies a DC current I from the positive terminal91 via the transmission line 1120 to the electric element 100, andreceives a return current Ir, which is supplied from the electricelement 100 via the transmission line 1140, at the negative terminal 92.

The electric element 100 receives the DC current I, which is suppliedfrom the power source 90 via the transmission line 1120, at the anodeelectrode 101, and supplies the received DC current I from the anodeelectrode 102 via the transmission line 1130 to the capacitor 160. Theelectric element 100 also receives the return current Ir, which issupplied from the capacitor 160 via the transmission line 1150, at thecathode electrode 104, and supplies the received return current Ir fromthe cathode electrode 103 via the transmission line 1140 to the powersource 90. In addition, the electric element 100 confines an unwantedhigh-frequency current transmitted from the capacitor 160 via thetransmission lines 1130, 1150 within circuitry made up of the electricelement 100, transmission lines 1130, 1150, capacitor 160 and CPU 110 inthe aforementioned manner, thereby preventing the unwantedhigh-frequency current from leaking toward the power source 90.

The capacitor 160 stores the DC current supplied from the electricelement 100 via the transmission line 1130, and supplies the stored DCcurrent through the transmission line 1170 to the CPU 110. The capacitor160 also supplies the return current Ir, which is supplied from the CPU110 via the transmission line 1180, through the transmission line 1150to the electric element 100.

The CPU 110 is driven with the DC current I supplied from the capacitor160 and operates at a predetermined frequency. The CPU 110 then suppliesthe return current Ir to the capacitor 160 via the transmission line1180.

FIG. 33 is a conceptual illustration showing the electric element 100shown in FIG. 32 in an operating state. Referring to FIG. 33, theelectric element 100 includes an anode electrode 10C connected to thetransmission line 1120 and an anode electrode 10D connected to thetransmission line 1130. The electric element 100 further includes acathode electrode 20E connected to the transmission line 1140 and acathode electrode 20F connected to the transmission line 1150.

With this configuration, a DC current I output from the positiveterminal 91 of the power source 90 flows through the transmission line1120 to the anode electrode 10C of the electric element 100 and flows inthe electric element 100 in order from the side anode electrode 10Athrough the conductive plates 11, 12 and side anode electrode 10B to theanode electrode 10D. The DC current I then flows from the anodeelectrode 10D via the transmission line 1130 and anode electrode 161 tothe capacitor 160.

The DC current I is stored in the capacitor 160 in such a way. Thecapacitor 160 supplies the stored DC current I to the CPU 110. The CPU110 is driven with the DC current I from the capacitor 160 and outputs areturn current Ir equivalent in magnitude to the DC current I. Thecapacitor 160 supplies the return current Ir, which is supplied from theCPU 110, to the electric element 100 through the transmission line 1150.

The return current Ir then flows through the transmission line 1150 tothe cathode electrode 20F of the electric element 100, and flows in theelectric element 100 in order from the side cathode electrodes 20C, 20Dthrough the conductive plates 21 to 23 and side cathode electrodes 20A,20B to the cathode electrode 20E. The return current Ir then flows fromthe cathode electrode 20E through the transmission line 1140 andnegative terminal 92 to the power source 90.

Since the DC current I flows in the conductive plates 11, 12 from thepower source 90 side to the CPU 110 side, while the return current Irflows in the conductive plates 21 to 23 from the CPU 110 side to thepower source 90 side in the electric element 100, effective inductance Lof the electric element 100 becomes small as discussed above. On theother hand, effective capacitance C of the electric element 100 becomeslarge due to the four capacitors being connected in parallel in theelectric element 100. Thus, the impedance of the electric element 100 islowered.

The CPU 110 is driven with the DC current I supplied from the powersource 90 through the electric element 100 and produces an unwantedhigh-frequency current. The unwanted high-frequency current is leakedthrough the transmission lines 1170, 1180 to the capacitor 160 andelectric element 100, however, the unwanted high-frequency current flowsin circuitry made up of the electric element 100, transmission lines1130, 1150, capacitor 160, transmission lines 1170, 1180 and CPU 110because of the low impedance of the electric element 100, therebypreventing the unwanted high-frequency current from leaking from theelectric element 100 toward the power source 90.

Under circumstances where the operating frequency of the CPU 110 tendsto shift toward high frequencies, it could be assumed that the CPU 110operates at approximately 1 GHz. Even for such a high operatingfrequency range, because the impedance of the electric element 100 isdetermined mainly by the effective inductance L that is decreased asdiscussed above, the electric element 100 can confine the unwantedhigh-frequency current produced by the CPU 110 operating at a highoperating frequency within the vicinity of the CPU 110. In short, theelectric element 100 prevents the leakage of the unwanted high-frequencycurrent toward the power source.

FIG. 34 is a perspective view illustrating the structure of thecapacitor 160 shown in FIG. 32. Referring to FIG. 34, the capacitor 160includes a tantalum sintered body 163, a dielectric oxide film 164,conductive polymeric layer 165, and a lead layer 166 in addition to theanode electrode 161 and cathode electrode 162. The capacitor 160 in thisembodiment has two terminals (i.e. one anode electrode and one cathodeelectrode), but may have three terminals (i.e. one anode electrode andtwo cathode electrodes) or four terminals (i.e. two anode electrodes andtwo cathode electrodes).

The dielectric oxide film 164 covers surfaces of the tantalum sinteredbody 163. The conductive polymeric layer 165 composed of polypyrrolecovers the dielectric oxide film 164. The lead layer 166 including acarbon layer and a silver paint layer covers the conductive polymericlayer 165. The carbon layer is formed so as to make contact with theconductive polymeric layer 165, while the silver paint layer is formedso as to make contact with the carbon layer.

The anode electrode 161 is connected to the tantalum sintered body 163,while the cathode electrode 113 is connected to the lead layer 166. Thetantalum sintered body 163 functions as an anode of the capacitor, andthe conductive polymeric layer 165 functions as a cathode of thecapacitor.

The capacitor having the structure shown in FIG. 34 is referred to asPOSCAP (Polymerized Organic Semiconductor Capacitors) and is a chipcapacitor using the tantalum sintered body for an anode and thehigh-conductive polymeric (polypyrrole) layer for a cathode. Thiscapacitor 160 (POSCAP) has a large capacity because the tantalumsintered body is porous.

This capacitor 160 (POSCAP) is fabricated in the following manner. Atfirst, the dielectric oxide film 164 of several hundreds of angstroms isformed on surfaces of the tantalum sintered body 163. Then, polypyrroleis polymerized to coat the dielectric oxide film 164. This provides theconductive polymeric layer 165.

Secondly, the carbon layer and silver paint layer are provided on theconductive polymeric layer 165 (polypyrrole layer). At last, the anodeelectrode 161 is connected to the tantalum sintered body 163 byresistance welding, and the cathode electrode 162 is connected to thelead layer 166 by silver adhesive. The capacitor 160 is thus completed.

Referring back to FIG. 32, the power source 90 supplies a DC current Ithrough the transmission line 1120 to the electric element 100. Theelectric element 100 allows the DC current I, which is supplied from thepower source 90, to flow from the anode electrode 101 (10C), through theside anode electrode 10A, conductive plates 11, 12, side anode electrode10B and anode electrode 102 (10D) to the transmission line 1130. Throughthe transmission line 1130, the DC current I is supplied to thecapacitor 160.

The capacitor 160 stores the DC current I supplied from the power source90 via the electric element 100 and supplies the stored DC current I tothe CPU 110 via the transmission line 1170.

The CPU 110 is driven with the DC current I supplied from the capacitor160 and operates at a predetermined frequency. The CPU 110 feeds areturn current Ir of the DC current I through the transmission line 1180to the capacitor 160. With the operation of the CPU 110, an unwantedhigh-frequency is generated and leaks through the transmission lines1170, 1180 toward the capacitor 160.

The capacitor 160 passes the return current Ir, which is supplied fromthe CPU 110, through the cathode electrode 162, lead layer 166 andconductive polymeric layer 165 to the transmission line 1150 thatsupplies the return current Ir to the electric element 100.

The electric element 100 passes the return current Ir, which is suppliedfrom the capacitor 160 through the transmission line 1150, via thecathode electrode 104 (20F), side cathode electrodes 20C, 20D,conductive plates 21 to 23, side cathode electrodes 20A, 20B and cathodeelectrode 103 (20E) to the transmission line 1140 that supplies thereturn current Ir to the power source 90.

Since the DC current I flows in the conductive plates 11, 12 of theelectric element 100 from the power source 90 side to the CPU 110 side,while the return current Ir flows in the conductive plates 21 to 23 ofthe electric element 100 from the CPU 110 side to the power source 90side, the effective inductance of the conductive plates 11, 12 becomessmaller than the self-inductance due to the mutual inductance betweenthe conductive plates 11, 12 and the conductive plates 21 to 23 asdiscussed above. As a result, the impedance of the electric element 100decreases.

The unwanted high-frequency current leaks from the CPU 110 to theelectric element 100 through the path made up of the transmission lines1170, 1180, capacitor 160 and transmission lines 1130, 1150 and passeswithin the electric element 100, but does not leak toward the powersource 90 through the transmission lines 1120, 1140. In other words, theunwanted high-frequency current leaked from the CPU 110 flows withincircuitry made up of the electric element 100, transmission lines 1130,1150, capacitor 160, transmission lines 1170, 1180 and the CPU 110,without flowing through the transmission lines 1120, 1140 toward thepower source 90.

In this manner, the electric element 100 confines the unwantedhigh-frequency current produced by the CPU 110 within the vicinity ofthe CPU 110. The capacitor 160 has a high capacity owing to the porousanode. This allows the capacitor 160 to quickly supply the DC current Ito the CPU 110 in response to rapid start-up of the CPU 110.

The present invention, as discussed above, realizes the rapid start-upof the CPU 110 by disposing the high-capacity capacitor 160 adjacent tothe CPU 110.

FIG. 35 is an another schematic view illustrating the structure of anelectric circuit according to the sixth embodiment. Referring to FIG.35, the electric circuit 1100A includes an electric element 101A havinga capacitor 160 thereon, instead of the electric element 100 of theelectric circuit 1100 shown in FIG. 32. The other components are thesame as those of the electric circuit 1100.

FIG. 36 is a cross-sectional view of the electric element 101A andcapacitor 160 shown in FIG. 35. Referring to FIG. 36, the electricelement 101A includes conductive plates 11A, 12A, 13A, 21A, 22A insteadof the conductive plates 11, 12, 21 to 23 of the electric element 100(see FIG. 4), and is added with a dielectric layer 6 and cathodeelectrodes 20G, 20H. The other components are the same as those of theelectric element 100.

Each of the conductive plates 11A, 12A, 13A, 21A, 22A is composed of Niand has a thickness in a range between 10 μm to 20 μm. Each of theconductive plates 11A, 12A, 13A has the same dimensions as theconductive plates 11, 12, while each of the conductive plates 21A, 22Ahas the same dimensions as the conductive plates 21 to 23. Thedielectric layer 6 is composed of BaTiO₃ and has the same dimensions asthe dielectric layers 1 to 5.

The conductive plate 11A is placed so as to abut on the dielectriclayers 1 and 2, while the conductive plate 21A is placed so as to abuton the dielectric layers 2 and 3. The conductive plate 12A is placed soas to abut on the dielectric layers 3 and 4, while the conductive plate22A is placed so as to abut on the dielectric layers 4 and 5. Theconductive plate 13A is placed so as to abut on the dielectric layers 5and 6, while the dielectric layer 6 is placed so as to abut on theconductive plate 13A.

The side anode electrode 10A is connected to one end of the conductiveplates 11A, 12A, 13A, while the side anode electrode 10B is connected tothe other end of the conductive plates 11A, 12A, 13A.

Although it is not shown in FIG. 36, the side cathode electrodes 20A,20B, 20C, 20D are connected to the conductive plates 21A, 22A. Thecathode electrodes 20G, 20H are connected to the side cathode electrodes20A, 20C, respectively.

In the capacitor 160, a conductive polymeric layer 165, dielectric oxidefilm 164, tantalum sintered body 163, dielectric oxide film 164 andconductive polymeric layer 165 are sequentially disposed in this orderfrom the closer side to the conductive plate 13A of the electric element101A. It is noted that the lead layer 166 of the capacitor 160 isomitted. Conductors 167, 168 are connected, through the lead layer 166,with the conductive polymeric layer 165 which is a cathode. In thestructure in which the capacitor 160 is mounted on the electric element101A, the conductors 167, 168 are disposed on cathode electrodes 20G,20H, respectively, of the electric element 101A. The cathode (i.e.conductive polymeric layer 165) of the capacitor 160 is thus connectedto the cathode electrodes 20E, 20F of the electric element 101A.Therefore, the conductors 167, 168 constitute the transmission line 1150shown in FIG. 35.

In the electric element 101A, a DC current I supplied from the powersource 90 flows in the anode electrode 10C, side anode electrode 10A,conductive plates 11A, 12A, 13A, side anode electrode 10B and anodeelectrode 10D in this order. In short, the DC current I flows throughthe conductive plates 11A, 12A, 13A in the direction of arrow 105.

Alternatively, a return current Ir supplied from the capacitor 160 flowsin the cathode electrode 20F, side cathode electrodes 20C, 20D,conductive plates 21A, 22A, side cathode electrodes 20A, 20B and cathodeelectrode 20E in this order. In short, the return current Ir flows inthe conductive plates 21A, 22A in the direction of arrow 106.

In the capacitor 160, the DC current I supplied from the electricelement 101A flows in the tantalum sintered body 163 (anode) in thedirection of arrow 105, while the return current Ir supplied from theCPU 110 flows in the conductive polymeric layer 165 (cathode) in thedirection of arrow 106.

For this configuration, the effective inductance of the conductiveplates 11A, 12A becomes smaller than their self-inductance under theinfluence of the mutual inductance generated by the return current Irpassing within the electric element 101A. The effective inductance ofthe conductive plate 13A also becomes smaller than its self-inductanceunder the influence of the mutual inductance generated by the returncurrent Ir flowing in the conductive plate 22A of the electric element101A and the return current Ir flowing in the conductive polymeric layer165 (cathode) of the capacitor 160. As a result, the impedance of theelectric element 101A is lowered.

As discussed above, the effective inductance of the electric element101A decreases with the mutual inductance derived from the returncurrent Ir flowing in the electric element 101A and the mutualinductance derived from the return current Ir flowing in the capacitor160, and consequently the impedance is lowered.

Thus, the electric element 101A can obtain the lower impedance than theelectric element 100. The electric element 101A, therefore, can confinefurther the unwanted high-frequency current produced by the CPU 110within the vicinity of the CPU 110. In other words, the electric element101A can prevent still more leakage of the unwanted high-frequencycurrent toward the power source 90.

As discussed above, the electric circuit 1100A is characterized in thatthe capacitor 160 is mounted on the electric element 101A and theconductive plate 13A (conductive plate where the DC current I flows) isplaced at the closest position to the capacitor 160. This characteristicfeature enables the electric element 101A, as discussed above, to makeits impedance lower than that of the electric element 100; consequently,the unwanted high-frequency current produced by the CPU 110 can befurther confined within the vicinity of the CPU. The placement of thecapacitor 160 on the electric element 101A can also reduce the area formounting both on a board.

In the above embodiment, the conductive plate 13A, in which the DCcurrent I passes, of the electric element 101A is arranged at theclosest position to the capacitor 160, because the capacitor 160 has theconductive polymeric layer 165, in which the return current Ir flows,arranged at the closest position to the electric element 101A. However,if the capacitor 160 has an electrode, in which the DC current I passes,placed at the closest position to the electric element 101A, theconductive plate 22A, in which the return current Ir flows, of theelectric element 101A should be disposed at the closest position to thecapacitor 160.

Of two direct currents flowing at the closest position in the electricelement 101A with respect to the capacitor 160 and flowing at theclosest position in the capacitor 160 with respect to the electricelement 101A in the electric circuit 1100A, either one should be the DCcurrent I and the other should be the return current Ir. The conductiveplate, to be placed closest to the capacitor 160, in the electricelement 101A is thus determined to satisfy the above condition.Specifically, the conductive plate, to be placed at the closest positionto the capacitor 160, of the electric element 101A passes a current inthe opposite direction to a current flowing in the conductive plate, tobe placed at the closest position to the electric element 101A, of thecapacitor 160.

Although all the dielectric layers 1 to 6 are composed of the samedielectric material (BaTiO₃) in the above embodiment, the presentinvention is not limited to this. The dielectric layers 1 to 6 can becomposed of different dielectric materials on an individual basis.Alternatively, the dielectric layers 1 to 6 can be put into two groupseach composed of the same material, but the materials are different toeach other. Typically the dielectric layers 1 to 6 may be composed ofone or more kinds of dielectric materials. Any dielectric material forforming the dielectric layers 1 to 6 preferably has the relativepermittivities of 3000 or more.

In addition to BaTiO₃, the dielectric layers may be composed ofBa(Ti,Sn)O₃, Bi₄Ti₃O₁₂, (Ba, Sr, Ca)TiO₃, (Ba, Ca)(Zr, Ti)O₃, (Ba, Sr,Ca)(Zr, Ti)O₃, SrTiO₃, CaTiO₃, PbTiO₃, Pb(Zn, Nb)O₃, Pb(Fe, W)O₃, Pb(Fe,Nb)O₃, Pb(Mg, Nb)O₃, Pb(Ni, W)O₃, Pb(Mg, W)O₃, Pb(Zr, Ti)O₃, Pb(Li, Fe,W)O₃, Pb₅Ge₃O₁₁, CaZrO₃, or the like.

FIG. 37 is a perspective view illustrating an exemplary electric circuitaccording to the sixth embodiment. FIG. 38 is a plan view of theelectric circuit viewed from direction A of FIG. 37. FIG. 39 is a planview of the electric circuit viewed from direction B of FIG. 37. FIG. 40is a plan view of the electric circuit viewed from direction C of FIG.37. FIG. 41 is a cross-sectional view of the electric circuit takenalong lines XXXXI-XXXXI of FIG. 37.

Referring to FIGS. 37 and 38, the electric circuit 1200 comprises anelectric element 1210, a capacitor 1220, a copper plate 1230, and resin1240. The electric element 1210 has the same structure as the electricelement 101 shown in FIG. 10, and includes anode electrodes 1211, 1212and cathode electrodes 1213, 1214. The anode electrodes 1211, 1212 areconnected to the copper plate 1230. The electric element 1210 is mountedon the capacitor 1220.

The capacitor 1220 has the same structure as the capacitor 160 shown inFIG. 34 and includes an anode electrode 1221. The anode electrode 1221is connected to the copper plate 1230.

The cathode electrodes 1213, 1214 of the electric element 1210 aredisposed on the front face 1200A, bottom face 1200B, rear face 1200C andtop face 1200D of the electric circuit 1200. A cathode electrode (notshown) of the capacitor 1220 is connected to the cathode electrode 1214of the electric element 1210.

The resin 1240 seals around the capacitor 1220 and a part of the cathodeelectrode 1214. The copper plate 1230 is shaped like a rectangle withoutone side in cross section and surrounds the electric element 1210,capacitor 1220 and resin 1240.

The copper plate 1230 has cut-away sections 1231, 1232. The cathodeelectrodes 1213, 1214 are partially disposed on the top face of theelectric element 1210 and within the area where the cut-away sections1231, 1232 of the copper plate 1230 are located (see FIG. 39).

The copper plate 1230 is arranged on opposite sides of the bottom faceof the electric circuit 1200. The cathode electrodes 1213, 1214 areplaced on the inside of the copper plates arranged on the opposite sides(see FIG. 40).

The cathode electrode 1214 is formed along the electric element 1210 butinwardly curved in an area in which the capacitor 1220 is placed. Thecurved parts of the cathode electrode 1214 make a connection with thecathode electrode of the capacitor 1220. The resin 1240 fillsinterstices between the electric element 1210 and capacitor 1220, underthe capacitor 1220, and the inside of the curved parts of the cathodeelectrode 1214 (see FIG. 41).

The electric circuit 1200 is disposed between the power source 90 andCPU 110 and performs the same functions as the aforementioned electriccircuit 1100A. Such an electric circuit 1200 has an anode electrode 1211and a cathode electrode 1213 connected to the power source 90, and anodeelectrodes 1212, 1221 and a cathode electrode 1214 connected to the CPU110.

Thus, the electric circuit 1200 allows the capacitor 1220 to store apower source current supplied from the power source 90 and to supply thestored electrical current to the CPU 110. The electric circuit 1200concurrently prevents the unwanted high-frequency current produced bythe CPU 110 from leaking toward the power source 90.

The above-discussed electric circuit according to the sixth embodimentcomprises the capacitor arranged between the power source and electricelement and the electric element arranged between the capacitor and CPUand having low impedance. Because of this configuration, the electriccircuit can store electric currents supplied from the power source andsupply it to the CPU as confining the unwanted high-frequency currentproduced by the CPU within circuitry made up of the electric element andCPU.

Accordingly, the present invention can prevent the leakage of theunwanted high-frequency current toward the power source, and alsorapidly start up an electrical load circuit.

The electric circuit 1100 according to the sixth embodiment can use anyone of the electric elements 101, 200, 300, 400, 500, 600, 700 and 800instead of the electric element 100.

The electric circuit 1200 according to the sixth embodiment can use anyone of the electric elements 100, 200, 300, 400, 500, 600, 700 and 800instead of the electric element 101.

The Seventh Embodiment

FIG. 42 is a schematic view of the structure of the electric circuitaccording to the seventh embodiment. Referring to FIG. 42, the electriccircuit 1300 of the seventh embodiment comprises electric elements 1310,1320. Both electric elements 1310, 1320 have the same structure as theelectric element 101 shown in FIG. 10. The electric element 1310includes anode electrodes 1311, 1312 and cathode electrodes 1313, 1314.The electric element 1320 includes anode electrodes 1321, 1322 andcathode electrodes 1323, 1324.

In the electric element 1310, overlap parts 20 of the conductive plates11, 12 and conductive plates 21, 22 have length L2 and width W2 so setas to hold W2≧L2. In the electric element 1320, overlap parts 20 of theconductive plates 11, 12 and conductive plates 21, 22 have length L2 andwidth W2 so set as to hold L2>W2. Thus, the electric element 1310functions as a capacitor, on the other hand, the electric element 1320functions as a noise filter.

FIG. 43 is a bottom view illustrating the electric elements 1310, 1320shown in FIG. 42. Referring to FIG. 43, the anode electrodes 1311, 1312are disposed on one side and the other side, respectively, both opposedto each other, of the electric element 1310 in the longitudinaldirection, while the cathode electrodes 1313, 1314 are disposed on theinside of the anode electrodes 1311, 1312. Specifically, the cathodeelectrode 1313 is disposed closer to the anode electrode 1311 than themidpoint between the anode electrodes 1311 and 1312, while the cathodeelectrode 1314 is disposed closer to the anode electrode 1312 than themidpoint.

The anode electrodes 1321, 1322 are disposed on one side and the otherside, respectively, both opposed to each other, of the electric element1320 in the longitudinal direction, while the cathode electrodes 1323,1324 are disposed on the inside of the anode electrodes 1321, 1322.Specifically, the cathode electrode 1323 is disposed closer to the anodeelectrode 1321 than the midpoint between the two anode electrodes 1321,1322, while the cathode electrode 1324 is disposed closer to the anodeelectrode 1322 than the midpoint.

FIG. 44 is a plan view illustrating a board on which the electriccircuit 1300 shown in FIG. 42 is mounted. Referring to FIG. 44, theboard 1330 has anode sections 1331 to 1333, grounding sections 1334 to1339, cut-away sections 1340 to 1344. The anode sections 1331 to 1333and grounding sections 1334 to 1339 are formed by forming cut-awaysections 1340 to 1344 in a conductor formed on the printed board.

The anode sections 1331, 1332, 1333 are formed in the cut-away sections1340, 1342, 1344, respectively. The grounding section 1336 is formedbetween the cut-away sections 1340 and 1341 and connected to the twogrounding sections 1334, 1335. The grounding section 1337 is formedbetween the cut-away sections 1341 and 1342 and connected to the twogrounding sections 1334, 1335. The grounding section 1338 is formedbetween the cut-away sections 1342 and 1343 and connected to the twogrounding sections 1334, 1335. The grounding section 1339 is formedbetween the cut-away sections 1343 and 1344 and connected to the twogrounding sections 1334, 1335.

Referring to FIGS. 42 to 44, the anode electrode 1311 of the electricelement 1310 is placed on the anode section 1331. The anode electrode1312 is placed on the anode section 1332. The cathode electrode 1313 isplaced on the grounding sections 1334, 1336, 1335. The cathode electrode1314 is placed on the grounding sections 1334, 1337, 1335.

The anode electrode 1321 of the electric element 1320 is placed on theanode section 1332. The anode electrode 1322 is placed on the anodesection 1333. The cathode electrode 1323 is placed on the groundingsections 1334, 1338, 1335. The cathode electrode 1324 is placed on thegrounding sections 1334, 1339, 1335.

This configuration allows the anode electrode 1312 of the electricelement 1310 to be electrically connected to the anode electrode 1321 ofthe electric element 1320 through the anode section 1332, while allowingthe cathode electrodes 1313, 1314 of the electric element 1310 to beelectrically connected to the cathode electrodes 1323, 1324 of theelectric element 1320 through the grounding sections 1334, 1335.

The electric circuit 1300 is used between the power source 90 and CPU110 and connected to the power source 90 on the anode section 1331 side,and to the CPU 110 on the anode section 1333 side. Consequently, theelectric element 1310 functioning as a capacitor is disposed near thepower source 90, while the electric element 1320 functioning as a noisefilter is disposed near the CPU 110.

Once the electric circuit 1300 is supplied with a power source currentfrom the power source 90, the power source current is stored in theelectric element 1310 (i.e. capacitor) and then supplied to the CPU 110through the electric element 1320 (i.e. noise filter). At the same time,the electric circuit 1300 confines the unwanted high-frequency currentproduced by the CPU 110 within circuitry made up of the CPU 110 andelectric element 1320 (i.e. noise filter).

Accordingly, the present invention can prevent the leakage of theunwanted high-frequency current toward the power source and rapidlystart up the electrical load circuit.

The electric circuit 1300 according to the seventh embodiment can useany one of electric elements 100, 200, 300, 400, 500, 600, 700 and 800instead of the electric element 101.

FIG. 45 is a schematic view illustrating the structure of the otherelectric circuit according to the seventh embodiment. The electriccircuit according to the seventh embodiment can be replaced with thiselectric circuit 1400 shown in FIG. 45. Referring to FIG. 45, theelectric circuit 1400 comprises electric elements 1410, 1420, 1430. Theelectric element 1410 includes an anode electrode 1411 and a cathodeelectrode 1412, each connected to one of conductive plates (not shown)which are opposed to each other. The two conductive plates of theelectric element 1410 have length L5 and width W5 (<L5) each. Theelectric element 1410 has an approximately rectangular plane andfunctions as a noise filter. The board 1440 includes grounding sections1441, 1443 and an anode section 1442.

FIG. 46 is a plan view of the two electric elements 1420, 1430 shown inFIG. 45. Referring to FIG. 46, the electric element 1420 includes ananode electrode 1421 and a cathode electrode 1422, each connected to oneof conductive plates (not shown) which are opposed to each other. Thetwo conductive plates of the electric element 1420 have length L6 andwidth W6 (L6). The electric element 1430 includes an anode electrode1431 and a cathode electrode 1432, each connected to one of theconductive plates (not shown) which are opposed to each other. The twoconductive plates of the electric element 1430 have approximately thesame dimensions as the two conductive plates of the electric element1420. Accordingly, the electric elements 1420, 1430 have approximatelyrectangular planes and function as a capacitor.

In the case where the two electric elements 1420, 1430 are mounted onthe board 1440, the anode electrode 1421 of the electric element 1420and the anode electrode 1431 of the electric element 1430 are arrangedon the anode section 1442, while the cathode electrode 1422 of theelectric element 1420 and the cathode electrode 1432 of the electricelement 1430 are arranged on the grounding section 1443. Between theelectric elements 1420 and 1430, a space 1450 is formed.

The electric element 1410 is placed on the two electric elements 1420,1430 which are mounted on the board 1440. In this configuration, theanode electrode 1411 of the electric element 1410 is arranged on theanode electrode 1421 of the electric element 1420 and the anodeelectrode 1431 of the electric element 1430, while the cathode electrode1412 of the electric element 1410 is arranged on the cathode electrode1422 of the electric element 1420 and the cathode electrode 1432 of theelectric element 1430. This configuration allows the anode electrode1411 of the electric element 1410 to be connected to the anode electrode1421 of the electric element 1420 and the anode electrode 1431 of theelectric element 1430, while allowing the cathode electrode 1412 of theelectric element 1410 to be connected to the cathode electrode 1422 ofthe electric element 1420 and the cathode electrode 1432 of the electricelement 1430.

FIG. 47 is a side view of the electric circuit 1400 shown in FIG. 45viewed from direction A. FIG. 48 is a bottom view of the electriccircuit 1400 shown in FIG. 45. The electric element 1410 is mounted onthe electric element 1430 and has the anode electrode 1411 connected tothe anode electrode 1431 of the electric element 1430 and the cathodeelectrode 1412 connected to the cathode electrode 1432 of the electricelement 1430 (see FIG. 47). The two electric elements 1420, 1430 aredisposed with space 1450 therebetween (see FIG. 48).

The electric circuit 1400 is used between the power source 90 and CPU110. The anode electrodes 1421, 1431 and cathode electrodes 1422, 1432of the electric elements 1420, 1430 are connected to the power source90, while the anode electrode 1411 and cathode electrode 1412 of theelectric element 1410 are connected to the CPU 110.

Once the electric circuit 1400 is supplied with a power source currentfrom the power source 90, the power source current is stored in theelectric elements 1420, 1430 (i.e. capacitor) and supplied through theelectric element 1410 (i.e. noise filter) to the CPU 110. At the sametime, the electric circuit 1400 confines the unwanted high-frequencycurrent produced by the CPU 110 within circuitry made up of the CPU 110and electric element 1410 (noise filter).

According to the present invention, the use of the electric element 1410having two terminals and the electric elements 1420, 1430 each havingtwo terminals can prevent the unwanted high-frequency current fromleaking toward the power source and allows the electrical load circuitto rapidly start up.

The electric circuit 1400 can properly work without either of theelectric element 1420 or 1403. The provision of the two electricelements 1420, 1430 functioning as capacitors is for mounting theelectric element 1410 with stability. The electric circuit capable ofpreventing the unwanted high-frequency current from leaking toward thepower source and supplying the electric current to the electrical loadcircuit can be fully achieved with the electric element 1410 and any oneof the electric elements 1420 and 1403.

In the present invention, the conductive plates 11, 12 constitute “afirst conductor”, while the conductive plates 21 to 23 constitute “asecond conductor”.

The conductive wires 501 to 503 constitute “a first conductor”, whilethe conductive wires 511, 512 constitute “a second conductor”.

The conductive wires 601 to 603 constitute “a first conductor”, theconductive wires 611 to 613 constitute “a second conductor”.

The CPU 110 is “an electrical load circuit”.

The side face 100A is “a first side face”, side face 100B is “a secondside face”, the front face 100D is “a third side face”, and the rearface 100E is “a fourth side face”.

In the present invention, the conductive plates 11, 12, 21 to 23, 201,202, 301, 302, 311, 312, 401, 402, 411, 412 can be typically composed ofmetallic materials containing nickel as a main material. The dielectriclayers 1 to 6 can be typically composed of ceramics containing BaTiO₃ asa main material.

In the present invention, the conductive plates 11, 12, 21 to 23, 201,202, 301, 302, 311, 312, 401, 402, 411, 412 are equivalent to conductivelayers.

It should be understood that the embodiments disclosed herein are to betaken as examples and are not limited. The scope of the presentinvention is defined not by the above described embodiments but by thefollowing claims. All changes that fall within meets and bounds of theclaims, or equivalence of such meets and bounds are intended to beembraced by the claims.

1. An electric element disposed between a power source and an electricalload circuit operating with an electric current from said power source,comprising: a first conductor through which a first current flows fromthe power source side to the electrical load circuit side; and a secondconductor through which a second current flows from the electrical loadcircuit side to the power source side; said second current being areturn current of said first current, wherein said first conductorcomprises n-number (n is a positive integer) of first conductive layers,each in the form of a flat plate, said second conductor comprisesm-number (m is a positive integer) of second conductive layers, each inthe form of a flat plate, opposed to said first conductive layer, saidn-number of first conductive layers and said m-number of secondconductive layers are alternately stacked, no conductive layer exists onan overlap area between the adjoining first conductive layer and thesecond conductive layer, said first current flows in the oppositedirection to said second current and does not flow in the same directionas said second current, said second current flows from one end side ofsaid second conductive layer to the other end side opposing to the oneend side on the whole of a region, which corresponds to said overlaparea, of said second conductive layer, and said first conductor has asmaller inductance than its self-inductance when said first and secondcurrents pass through said first and second conductors, respectively. 2.The electric element according to claim 1, further comprising:dielectric layers each disposed between said first conductive layer andsaid second conductive layer, wherein each of said n-number of firstconductive layers passes said first current that is a power sourcecurrent, and is sandwiched between two of said second conductive layersconnected to ground potential.
 3. The electric element according toclaim 2, wherein letting W be a length of said first and secondconductive layers in the direction perpendicular to the flow directionof said first and second currents and letting L be a length of saidfirst and second conductive layers in the direction in which said firstand second currents flow, an overlap part between said first conductivelayer and said second conductive layer holds W≧L.
 4. The electricelement according to claim 2, further comprising: a first electrodeelectrically connected to one end of said n-number of first conductivelayers in a first direction in which said first current flows throughsaid first conductive layers; a second electrode electrically connectedto the other end of said n-number of first conductive layers in saidfirst direction; a third electrode electrically connected to one end ofsaid m-number of second conductive layers in a second direction in whichsaid second current flows through said second conductive layers; and afourth electrode electrically connected to the other end of saidm-number of second conductive layers in said second direction.
 5. Anelectric circuit, comprising: an electric element according to any oneof claims 1 and 2 between a power source and an electrical load, whereinsaid plurality of first conductive layers make up a path through whichthe first current flows from said power source side to said load side,and said plurality of second conductive layers make up a path throughwhich the second current, being a return current of said first current,flows.